1878. J MR. E. J. MIERS ON THE PEN.EID.E. S05 



with some hesitation to this species, in the Museum collection. The 

 rostrum is of the form described by Milne-Edwards, but reaches but 

 little beyond the peduncle of the antennules, and scarcely at all be- 

 yond the antennal scale. The fifth pair of legs is considerably 

 longer than the preceding, and very slender ; the dactylus small, 

 of the usual form. This species cannot be the male sex of P. 

 dobsoni, described above, as it differs in the form of the postabdo- 

 minal segment, which is rounded at its antero-lateral angle, in the 

 existence of spines on the lateral margins of the last postabdominal 

 segment, &c. The median dorsal carina is prolonged to the poste- 

 rior margin of the cephalothorax ; and there is a raised lateral hue on 

 each side, extending from a point immediately above the antennal 

 spine halfway to the posterior margin. 



If the genus Xiphopeneus of Smith (Trans. Conn. Ac. ii. p. 26, 

 1871) be sustained, it will probably be necessary to refer this 

 species to it, as it agrees in the form of the rostrum, aud in the length 

 of the legs of the fifth pair, although the dactylus is quite short. 



Peinleus kroyeri. 



Peneus kroyeri, Heller, Wien. Akad. Wissensch. Sitzungsb. xlv. 

 (Abth. i.), p. 425, pi. ii. fig. 51 (1862). 



Xiphopeneus harttii, Smith, Trans. Conn. Ac. ii. p. 28, pi. i. 

 fig. 1 (1871). 



I have little hesitation in referring the Xiphopeneus harttii of 

 Smith, from Caravelhas, Bahia, to the previously described P. kroyeri 

 of Heller, from Rio Janeiro. A comparison of the figures and de- 

 scriptions will, I think, suffice to establish their identity ; and there 

 is a specimen from the West Indies in the British-Museum collection 

 which appears to belong to the same species. The genus Xipho- 

 peneus was characterized by its author mainly by the long and slender 

 antennules (which have a small lamelliform appendage which is not 

 foliaceous and expanded over the eye as in Penceus), the form of the 

 cephalothoracic sulci, aud the great length of the fourth and fifth 

 thoracic legs (which have the terminal joints slender and flagelliform 

 or, rather, styliform). The mouth-organs, antennae, &c. are not 

 different from those of Penceus. 



It will be seen that these characters are not of greater value than 

 those which distinguish the Pencei of Milne-Edwards's first aud second 

 sections (which have never been considered of generic importance). 

 Moreover the length of the posterior legs is certainly a character 

 that varies in the different species ; and in one (P. styliferus) already 

 referred to, which agrees in most of its characters with Xiphopeneus, 

 the dactylus of the fifth pair of legs is quite short. Nor do we know 

 at present how far these peculiarities are dependent upon the sex of 

 the animals (the specimens of P. kroyeri and P. styliferus in the 

 Museum collection are both males). 



If the genus Xiphopeneus be retained as distiuct, it will be neces- 

 sary to constitute more than one other new generic division for species 

 hitherto included in Penceus ; and as the materials at present existing 



Proc. Zool. Soc— 1878, No. XX. 20 



