136 BULLETIN OF THE 



rent channels meet at the middle of the endostome, which has there a 

 triangular projection, and a deep notch in its vertical, laminiform wall. 

 The meros-joint of the external maxillipeds is acutely produced forward 

 at its internal angle, and behind it the palpus is entirely concealed. The 

 epistome is very short. The eyes are small, and may be retracted into 

 their deep sockets so as to be almost entirely concealed. The basal joint 

 of the external antenna? is somewhat shorter than the next joint. ' 



The remarkable form of the endostome and external maxillipeds in this 

 genus indicates an approach to the oxystomatous crabs, to which the Par- 

 thenopidae show, indeed, considerable resemblance in other respects. 



Mesorhoea sexpinosa nov. sp. 



Carapax one fifth broader than long, and about equally produced hi 

 front and behind beyond the line of the lateral angles. Surface punc- 

 tate and inconspicuously pubescent. Protuberances of the gastric, car- 

 diac, and branchial regions strongly angular, each surmounted by a 

 three-sided spine, the spine of the branchial region being situated on the 

 postero-lateral margin, of which it forms a projection. The angles or 

 ridges are more or less crenulated. The lateral edges of the gastric 

 protuberance are continued forward nearly to the front, becoming parallel 

 shortly after diverging from the spine. The cardiac spine is more slender 

 than the others, and its posterior edge is nearly vertical. - The branchial 

 ridge is nearly straight. Between the protuberances and ridges the sur- 

 face is more or less regularly concave, the sides of the protuberances being 

 not swollen. The rostrum is short. The margins of the carapax are sub- 

 laminiform and almost entire, the normal crenulation being indicated only 

 by faint impressed lines on the limb. Microscopic n tches may, however, 

 be detected on the antero-lateral margin, which is slijitly convex toward 

 the lateral angle. Postero-lateral margin concave. Posterior margin about 

 half as long as the postero-lateral, convex at the middle, and terminating 

 on either side in a slight tooth. Afferent channels deep, separated from 

 the subhepatic channels by a very thin and sharp, prominent, ciliated 

 lamina, and defined on the inner side by the ciliated outer edge of the 

 ischium of the external maxillipeds. From the anterior angle of the 

 buccal area a short ridge extends to the middle of the inner tooth of 

 the orbit, which ridge separates the concavity of the epistome from that of 

 the subhepatic region. Meros-joint of the external maxillipeds with two 

 tubercles on the surface, one towards the postero-exterior angle, the 

 other close to the antero-exterior angle ; anterior margin of the joint 

 deeply concave or notched. Chelipeds short, pubescent, especially on the 

 toothed edges ; surface between the edges smooth ; on the basal joint 



