84 Mr. C. Spence Bate on Diastylis bicornis. 



by the dredge, in the summer before last, at the Shetlands ; but 

 Mr. Jeffreys, from whom I received it, has not recorded the 

 exact position or depth at which it was taken. 



Diastylis bicornis. PI. I. fig. 2. 



The carapace is less than a third of the length of the animal, 

 and pointed in front to a blunt rostrum. It is furnished laterally 

 upon each side, in a line with the dorsal eye, with a small an- 

 teriorly projecting tooth, behind and a little outside of which is 

 a second much larger tooth, which, together with the one upon 

 the opposite side of the carapace, gives the double-horned cha- 

 racter to the species, from which the name is derived. In the 

 posterior or cardiac region of the carapace, a little on each side 

 of the median line, is a small spine. The lateral walls or 

 branchial regions are thickly studded with small pointed teeth 

 or spines, planted in short rows in a direction vertical to the 

 lateral margins, the spines becoming more feeble and ultimately 

 dying out as they approach towards the dorsal surface. These 

 spines are all directed forwards, and are most abundant as well 

 as most important in size near the hepatic region, anterior to 

 which they again diminish in proportion. 



The pereion exposes dorsally four perfect somites posterior to 

 the carapace, of which the posterior is the longest. All are 

 smooth and free from ornamentation. 



The pleon is long and slender, the first somite being nearly 

 as long as broad ; the second, third, and fourth each gradually 

 increase in length, and are all furnished near the postero-lateral 

 extremity with a few cilia. The fifth somite is still narrower and 

 longer ; the sixth is as long as the fifth, but increases in breadth 

 posteriorly to furnish points for the articulation of the posterior 

 pair of pleopoda. 



The telson is long and narrow, being lanceolate and tipped 

 with a long process that is ciliated upon each side. 



The eye is small, and dorsally placed. The antennae are 

 small, or supposed to be so, since they are not discernible in 

 our unique specimen. The first pair of pereiopoda reach to 

 some distance beyond the extremity of the rostrum. The last 

 three pairs are uniform in shape and size, and terminate in 

 pointed but not very powerful dactyli and a few corresponding 

 cilia. 



The pleon in our specimen is not supplied with appendages ; 

 and the entire animal is about half an inch in length. 



It was dredged with the preceding; but neither the exact 

 locality in the Shetlands nor the depth at which it was taken 

 has been recorded. 



