1857.] HUXLEY PYGOCEPHALUS COOPERI. 363 



PeneidcB, although certain forms, as Stenopus, possess one, the other 

 characters are quite dissimilar; moreover, the flattened scale above the 

 antennae, characteristic of all these families, appears to be wanting in 

 our specimen, for I am inclined to consider the long subtrigonal frag- 

 ment lying in front of the eye (and which possibly might be regarded 

 as such) as a portion of one of the limbs, which has been displaced. 



Neither among "les Crustaces Cuirassees " can it be referred to 

 either of the genera Galathea, Eryon, or Palinurus : its general cha- 

 racters distinguish it from the first ; the material difference in the width 

 of the carapace, from the second; and the general form of the body, 

 together with the absence of spines on the carapace, and more especially 

 of the two prominent horns extending over the eyes and base of the 

 antennae, from the last. 



The flatness of the carapace, and the remoteness of the eyes, are 

 points of agreement with the genus Scyllarus ; but on the other hand, 

 in this specimen at least, there are no traces of the large expanded 

 antennae, which are so conspicuous in the latter. With regard to the 

 last division, that of the Astacidce, we need only select for comparison 

 the genus NepJu^ops, which has a similar cervical furrow, a median 

 ridge, running the whole length of the carapace, and two parallel 

 lateral ones on the hinder half. In addition to this, the abdominal 

 segments have very similar sculpturings. The position of the eye, 

 however, in Nephrops, the convexity of the carapace, and its being 

 overlapped by the first abdominal segment, are important differences. 



In conclusion, I would remark that, although the characters are 

 sufficiently well defined to render the genus and species identifiable 

 by the description and figure given, and although in some respects 

 there are indications of an affinity wdth Nephrops and Scyllarus, I 

 do not think the evidence sufficient to justify me in assigning it to 

 any existing genus of the Macrura. 



I therefore propose to constitute it the type of a new genus, with 

 the appellation of Tropifer'^, with the following, for the present neces- 

 sarily incomplete, characters : — 



Carapace flattened, keeled, slightly longer than broad, truncate 

 in front, and having the posterior angles slightly produced ; eyes 

 large, remote ; abdomen somewhat flattened, sculptured. 



The specific name Icevis is in allusion to the smoothness of the 

 carapace. 



2. Description of a New Crustacean (Pygocephalus Cooperi, 

 Huxley) from ^^e Coal-Measures. By Prof. Huxley, F.R.S., 

 F.G.S. 



[Plate XIIL] 



The following account of a very remarkable new Crustacean has 

 been drawn up from the examination of three specimens, two of 



* From rpoTTis, keel, and 0ep<u, / bear. 



