22 THE VOYAGE OF H.M.S. CHALLENGER. 



region of segments. Abdominal segments all fused to form a single oval piece which 

 terminates posteriorly in a short pointed extremity. Antennules with a long flagellum 

 reaching some way along the terminal joint of the peduncle of the antennae. 

 Antennas as long as the body; flagellum longer than the peduncle; third joint of 

 peduncle with a rudimentary exopodite ; two last joints of peduncle elongated. 

 Mandibles with a three-jointed palp. Thoracic appendages (in the female) not 

 dissimilar to each other, terminating in a single claw. Uropoda moderately long, 

 biramose, outer ramus one-jointed, inner with a small distal and long proximal joint. 



This genus comes nearest perhaps to Janira, but is to be distinguished by the 

 uniunguiculate thoracic appendages. The general shape of the body is also unlike 

 Janira, though in most other particulars it is hard to find any great differences between 

 the two genera. The presence of a rudimentary exopodite on the antennas is a feature 

 only found in this genus, in Janira, and in Stenetrium, where it has the form of a flat 

 scale tipped with fine hairs. In other genera this structure is entirely absent, though, as 

 I have already pointed out (p. 17), a stout spine occupying the same position in 

 lolanthe and Acanthoniscus may be its representative. 



Trichopleon ramosum, F. E. Beddard (PL I. figs. 1-10). 



Trichopleon ramosum, Proo. Zool. Soe. Lond., 1886, pt. i. p. 106. 



This species, as already mentioned, is represented by only a single individual, 

 dredged to the south of the Philippine Islands in 500 fathoms. 



The specimen is an immature female and measures 5 mm. in length ; it has been 

 stained in picrocarmine and mounted on a slide in Canada Balsam ; the sex was 

 ascertained by an examination of the ovaries, which Were darkly stained and very con- 

 spicuous in consequence ; one of these is shown in fig. 7 of PI. I. ; at the two 

 extremities the ovary is formed of indifferent tissue, in the middle is a single row of 

 ova, each surrounded by a follicular layer in which the constituent cells could not be 

 made out. The oviduct which arises at the end of the posterior third is pear-shaped 

 and opens by a slit-like orifice upon the last thoracic segment but two, near to the 

 attachment of the limbs. There were no traces of brood lamellae developed in this 

 specimen. 



The head is rather narrower but longer than the succeeding segment of the thorax ; 

 the insertion of the antennules is marked by a deep notch ; between the two antennules 

 the head is prolonged into a frontal process which ends squarely. To the outside of the 

 antennules the lateral region of the head is prolonged forwards, terminating in a blunt 

 rounded process which is almost exactly on a level with the frontal margin of the head. 

 There is no trace whatever of eyes. 



