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



the Devonian genus Dictyocaris, Salter, in which a distinct external sculpturing has also 

 been described ; but whether this resemblance is only accidental or points to some nearer 

 relationship between the two genera, it is impossible at present to say with any approach 

 to certainty. 



2. Nebaliopsis typica, n. sp. (PI. III.). 



Specific Characters. — Carapace thin and flexible, somewhat compressed, with a slight 

 dorsal keel running along the middle, its form, as seen laterally, oblongo-triangular, dorsal 

 line very faintly curved, anterior extremity narrowly rounded, posterior obtusely produced 

 above, inferior edges strongly curved in front of the middle. Eostral plate exceedingly 

 small, oval in form, with a slight carina running along the middle and terminating in a 

 blunt point. Surface of carapace sculptured by elevated narrow ridges anastomosing 

 with each other and forming together a somewhat irregular open network, less distinct 

 on the anterior part, where a somewhat flexuous transverse elevation passes down the 

 sides for a short distance from the anterior edge. Trunk very large, about as long as 

 pleon and tail combined. Tail scarcely longer than the three posterior segments of pleon 

 taken together, very narrow, with the posterior edge of the segments indistinctly denti- 

 culate. Eyes exceedingly small, cylindrical, smooth, apex rounded. Antennuke with 

 the two first joints of peduncle rather strong and subequal in length, third much smaller, 

 lamellar appendage about as long as first joint of flagellum. Antennas with the peduncle 

 scarcely longer than that of the antennulae, first joint the largest. Pleopoda with basal 

 part smooth, outer branch shorter than inner and having the outer edge strongly curved 

 and armed with a single row of small denticles. Caudal lamellae about as long as tail, 

 expanded in the middle, extremity tapering and slightly incurved, outer edge apparently 

 armed with seven spines, increasing in size posteriorly, tip with two spines (or strong 

 setas). Length reaching about 40 mm. 



Remarks. — The specific diagnosis given above is of course only provisional, the present 

 form being the only one of the genus as yet known. Most of the characters mentioned 

 above may, however, from analogy with other forms prove to be really specific in value. 

 It is apparently this form that was mentioned by the late Dr. v. Willemoes Suhm in a 

 letter to Professor v. Siebold, 1 as a gigantic Ostracode. This strange mistake may be 

 readily explained by the incompleteness of the first specimen obtained, of which only the 

 carapace and a small fragment of the body was brought up in the dredge. 



Description. — Of this remarkable form there is in the collection an apparently young 

 specimen with most of the limbs preserved, and also the carapace of a much larger and 

 in all probability adult specimen, together with a fragment of the cephalic part. The 

 former specimen has a length of 22 mm. excluding the caudal rami, which are wanting 



1 Zcitschr. f. wiss. Zool, BJ. xxiv. p. xiii. 



