FAMILY TIRONIDE.

GEN. TIRON, Lilljeborg.

1865. Tiron, Lilljeborg, N. Acta Soc. Upsal., Ser. 3, vol. vi., p. 19. 1906. Tiron, Stebbing, Das Tierreich, Amphipoda, pp. 275, 727.

The three species which the genus now includes may be distinguished as follows:

The new species has interesting peculiarities of the first maxillæ, and is further distinguished from T. acanthurus by a different shape of the second joint in the fifth peræopods, but these features are less easy to observe than those above given.

TIRON AUSTRALIS, n. sp.

Plate XXXVIII.

The general appearance closely agrees with that of T. acanthurus, the head having a deflexed rostrum, the first three segments of the pleon being postero-dorsally pluri-denticulate, and the fourth and fifth each produced into a dorsal tooth, but here the tooth of the fourth segment is much the shorter. The sixth segment has a scarcely perceptible tooth, flanked on each side by two spines. The anterior side-plates are finely crenate, the first and fourth smaller than the second and third.

The upper eyes are closely adjacent at the top of the head, each composed of about ten cones, of which each lateral eye has only four.

The first antennæ have the third joint shorter than the second, and the second much shorter than the first. The flagellum is somewhat longer than the peduncle, 9-jointed in the female specimen, 7-jointed in the male, the first joint in the latter being distinguished by its superior length and setose armature. The accessory flagellum

is 6-jointed in the female, 5-jointed in the male specimen. The second antennæ have an 8-jointed flagellum, shorter than the peduncle.

The mandibles differ slightly one from the other, the accessory plate on the left being, as so often, the stronger; it is succeeded by a row of 10 spines, the number on the right mandible being apparently only 8. The molar is strong, the palp slender, its third joint. half as long as the second, and armed only with three apical setæ. In the first maxillæ the inner plate is fringed with 9 plumose setæ, of which three at the apex are separated by a clear unarmed space from the other six. This is the case in both members of the pair, and could be seen in readiness for reproduction at the next exuviation. On the outer plate only 10 spines could be distinguished. The palp has a large second joint, much widened in its distal half, the apical margin fringed with 5 furcate spine-teeth and an outer spine-tooth which is serrate instead of furcate, with the serration on its inner side. In the furcate teeth the shorter tooth is the outer. The second maxillæ have the inner plate shorter but broader than the outer, with an oblique fringe of slender spines near the inner margin.

The gnathopods are scarcely distinguishable from those of T. acanthurus, the fifth joint long and slender, slightly tapering distally.

The peræopods are all alike in the shortness of the sixth joint, against which the small finger folds back closely, so that it becomes difficult to distinguish. Apparently it has a dorsal denticle. In all the pairs the fourth joint is larger than the fifth, this in the first and second pairs being but little longer than the sixth, but in the following pairs more and more surpassing it. In the third and fourth pairs the second joint is widely expanded, more so distally than proximally, but in the fifth peræopod this joint is widest proximally, and is roughly squared above, so as to differ much from the rounded appearance presented by the homologous joint in T. acanthurus. The marsupial plates of the female specimen are extremely narrow, their ovigerous function being probably aided by the long branchial vesicles.

The first and second uropods have the peduncle longer than the rami, which are nearly equal to one another in the first pair, but more unequal in the second, in neither very elongate. In the third pair the rami are much longer than the peduncle, the inner the shorter, fringed with long setæ, the outer carrying numerous spines.

The telson is subequal in length to the outer ramus of the third

uropod, cleft nearly five-sixths of its length, tapering, with a row of five or six spines standing up along the surface of each division, with accompanying setæ or setules, of which there are some also on the outer margins.

The male specimen is about 6 mm. long; the considerably larger female was about 8 mm. in length.

Locality. Lat. 33° 9′ 30′′ S., long. 28° 3' 00" E., dredged in a depth of 47 fathoms.

The specific name directs attention to the southern origin of this form, which presents so many points of resemblance to the northern T. acanthurus, from which, however, it is separated by some very marked differences. A comparison with Pseudotiron bouvieri, Chevreux, from the Mediterranean, is also of interest, but there the organs of vision and the minute third joint of the mandibular palp supply characters of generic distinction.

FAMILY GAMMARIDÆ.

GEN. CERADOCUS, Costa.

1853. Ceradocus, Costa, Rend. Soc. Borbon., n. ser., vol. ii., p. 170.

1906. Ceradocus, Stebbing, Das Tierreich, Amphipoda, p. 430.

CERADOCUS RUBROMACULATUS (Stimpson).

1855. Gammarus rubromaculatus, Stimpson, P. Ac. Philad., vol. vii., p. 394.

1906. Ceradocus rubromaculatus, Stebbing, Das Tierreich, Amphipoda, p. 430.

Locality. Lat. 33° 49' S., long. 25° 56' E. Two specimens were dredged from a depth of 24 fathoms, on rocky ground. One of the specimens has the second gnathopods very unequal and dissimilar, but, as noticed in the report on the Amphipoda of the Challenger, this appears to be the case not unfrequently in this species.

GEN. ELASMOPOIDES, n.

Most of the superficial characters as in Elasmopus, but (in female) first antennæ not longer than second, accessory flagellum elongate. Palp long in mandibles and maxillipeds. Inner plate on inner margin fringed with numerous setæ in first and second maxillæ. Second gnathopod powerful in female.

ELASMOPOIDES CHEVREUXI, n. sp.

Plate XXXIX.

Head not rostrate, obtusely produced at the sides. Back smooth, with saddle-shaped depression of fourth pleon segment. First sideplate the largest, broadly rounded at the produced front, fourth shallowly excavate behind, fifth and sixth each with a small front lobe curving backward. First three segments of the pleon with postero-lateral angles acute, a little produced, those of the third segment least so. Eyes dark, of peculiar shape, the broad lower part occupying the lateral lobes of the head, a narrower upper part ascending at right angles to the lower, so that the eyes are not far apart at the top.

First antennæ having two ridges on first joint, one ending in a spine, the other in a little tooth, second joint as long as first, third quite short, flagellum longer than peduncle, 42-jointed, accessory flagellum more than half as long as primary, 23-jointed. Second antennæ subequal in length to first, fifth joint of peduncle a little shorter than fourth, flagellum shorter than peduncle, 25-jointed.

Upper lip with front margin almost symmetrically rounded. Lower lip with principal lobes broad, inner plates well developed. Mandibles with cutting edge strongly toothed, secondary plate on left mandible stronger than that on right, teeth not prominent, spines of spine-row numerous, molar prominent, second and third joints of palp elongate, each with two rows of slender spines; the articular condyle between the molar and the palp very conspicuous. First maxilla with inner plate large, oblong, fringed on inner margin with very numerous setæ, outer plate with the spines crowded together, probably 11, some of them furcate; second joint of palp long, fringed with 7 apical spines, some of which are moderately stout, and 6 subapical, all slender. Second maxilla having the outer plate rather longer but narrower than the inner, fringed round the apex, the inner plate with a fringe along inner margin continued only a little way round the broad apex, and an oblique row of seta-like spines extending from near the apex to the proximal end of the marginal fringe. Maxillipeds with inner plates broad, fringed on inner and distal margins, the latter having three small spine-teeth at its inner part, outer plates not reaching middle of palp's long second joint, fringed. with numerous spines and spine-teeth; fourth joint of palp long, finger-like, curved, finely spinulose on inner margin, as long as the third, shorter than the second joint.

First gnathopods. Second joint with a row of setæ on distal part

of front margin, third and fourth joints very short, fifth and sixth joints subequal in length, spinose on both margins, the broad hinder prominence of the fifth having pectinate spines as well as long smooth ones, the sixth with gently convex front margin, the long, finely denticulate palm forming a much stronger convexity with the hind margin, from which it is marked off by palmar spines and the cessation of the denticulation; finger smooth, curved, matching the palm.

Second gnathopods much stronger than the first; second to fourth joints nearly as in preceding pair, fifth joint short, cup-shaped, sixth massive, widening to the palm, which is finely denticulate on either side of a somewhat semicircular cavity of variable depth and defined by a strong tooth, within which the finger closes, inner edge submarginally setiferous, outer edge proximally indented at four points for minute spines; finger strong, curved, inner margin with a small projection over the palmar gap.

First and second peræopods, slender, similar, but the first decidedly longer than the second, the second joint slightly curved, carrying long setæ at some points of the hind margin; the finger short, abruptly truncate at junction with the small nail.

Third to fifth peræopods stoutly built, fourth the longest, fifth longer than third; second joint with hind margin strongly dentate, especially and irregularly in the fifth pair, fourth and fifth joints. broad, with numerous spines, the sixth narrow but also spinose, all these joints having the front margin flattened; finger not very large, with regular curve to the nail.

Pleopods. Peduncle large, with apical process, the coupling hooks slender; the rami narrow, outer the shorter, having in the first pair 24 joints, while its considerably longer companion is 23-jointed, with 4 cleft spines on inner margin of the first joint.

First uropods with peduncle subequal to inner ramus, outer rather shorter, all with spines at intervals; second pair with rather shorter but stouter peduncle, as long as the inner ramus, the outer notably shorter; third pair with short peduncle, carrying on the surface facing inwardly a row of spinules and a tubercle beset with spines. and spinules; the rami broad, equal, strongly spined apically and on other parts; they are longer than their peduncle, but shorter than the other rami.

The telson is nearly as long as the peduncle of the third uropods, cleft to the base, the almost cylindrical halves somewhat divergent, with the truncate apices beset with terminal spines, the sides smooth except for a group of little spinules high up on the outer margin.