REPORT ON THE CRUSTACEA MACRURA. 163 



pleon slightly narrower than the carapace, median dorsal line carinated ; ophthalmo- 

 potla rudimentary, not lodged in a notch in the dorsal surface of the carapace, but 

 situated in the metope and not produced beneath the latero-anterior angle of the 

 carapace. 



First pair of antennas having the first joint of the peduncle produced to a scaledike 

 process, which, being laterally compressed against the corresponding margin of the 

 opposite appendage, is forced upwards into a crest-like ridge. The two succeeding joints 

 are cylindrical, and the last supports two very unequal flagella. 



The second pair of antennas carries a pointed, ovate scaphocerite and a long terminal 

 flagellum. The mandible has a serrate margin to the psalisiform blade, and carries a 

 Particulate synaphipod, but no molar tubercle, or ridge. The first and second pairs of 

 gnathopoda have no ecphysis, but the second pair carries a moderately long mastigo- 

 branchia. 



The pereiopoda are all chelate in both sexes ; the anterior pair is long and slender, the 

 posterior short and moderately robust. 



The pleopoda, excepting the first pair, which is modified according to sex, are biramose. 

 The rhipidura is well developed, the outer rami being broad and strong ; the telson 

 triangular, tapering, and terminally pointed. 



Geographical Distribution. — This genus has been taken in the Mediterranean Sea, 

 in the middle of the North and South Atlantic Oceans, and in the Pacific at a 

 distance of about 500 miles from the south-western coast of South America, at 

 depths ranging from 1300 to 2000 fathoms. The chief structural features that separate 

 the species in this genus from their congeners are the form and position of the 

 ophthabnopoda. 



Willemcesia leptodactyla (Pis. XVIII. , XIX., XX.). 



Willemossia leptodactyla, "Willemoes-Suhm, Trans. Linn. Soc. Lond., ser. 2, vol. i. p. 50; 



Sp. B., Rep. Brit. Assoc, 1878; Ann. and Mag. Nat. Hist., ser. 5, vol. ii. p. 280 



and pp. 484-7, 1878. 

 Deidamia leptodactyla, Willemoes-Suhm, Notes from the " Challenger," pt. 2, Nature, vol. viii. 



p. 51, May 15, 1873. 



The carapace has the lateral margins subparallel, slightly approximating anteriorly 

 and posteriorly. The antero-lateral angles are produced anteriorly to a sharp tooth that 

 reaches beyond the centre of the frontal margin. The frontal margin is furnished anteriorly 

 with an obliquely-directed rostral tooth, on one side of which, within the inner angle of 

 the orbital notch, is a small solitary tooth ; beyond it the margin to the outer angle is 

 smooth. The median dorsal ridge is armed with six or seven strong teeth anterior to the 

 cervical fossa, and four or five posterior to it. The lateral margins are separated into 



