88 Mr. C. Spence Bate on Nannastacus binoculoides. 



basal joint, equalling in length the basis of the pereiopod, and 

 a terminal flagellum formed of many minute articuli, each of 

 which supports strong cilia. 



The entire animal is ornamented with numerous closely packed 

 minute tubercles or coarse granules. They are most abundant, 

 but least conspicuous, on the carapace, where they appear to 

 culminate on the dorsal median line, being largest on the poste- 

 rior ridge of the anterior somites of the pleon ; they increase on 

 the dorsal surface into short spines ; the coxse and bases of the 

 four anterior pairs of pereiopoda are also conspicuously granu- 

 lated. 



This little Crustacean, which is about the eighth of an inch 

 in length, differs from the true Diastylidse in several important 

 particulars, all of which distinctions conduce to the opinion that 

 it stands in the animal kingdom at a grade higher, or, to speak 

 more correctly, in a position nearer to the true Macrura. 



It will be seen that the eyes are two, and separated widely 

 apart; but they differ from the Macrurous type in being 

 sessile and attached to the anterior portion of the carapace : in 

 this respect they differ from the same organs in the true Ma- 

 crura, since those are pedunculated, and, even in the larval 

 condition, exist as free organs independent of, though closely 

 protected by, the tissues of the carapace. 



In all the Diastylidse that have been hitherto described, the 

 antero-lateral processes of the posterior portion of the carapace 

 pass before and meet in front of the anterior portion of the 

 carapace, enclosing it so as to bring it near the centre of the 

 carapace. In the animal now described these lateral processes 

 reach but little beyond the eyes ; but we see, as it were, an effort 

 to fulfil the same conditions in the prolongation of the inferior 

 angle beyond the superior, whereas in the Macrurous type this 

 is considerably rounded off. 



It is to be regretted that this solitary specimen has alone 

 been obtained firom the numerous dredgings on the coast of 

 Shetland; but it is to be hoped that, since now attention is 

 drawn to the creature, we may be able to obtain more of an 

 animal which, from its intermediate character, may offer in dis- 

 section conditions of considerable interest, that may assist in 

 unravelling the mystery of some of the lost parts of certain fossil 

 Crustacea. 



EXPLANATION OF PLATE I. 



Fig, 1. Diastylis echinatus. 



Fig. 2. Diastylis bicornis. 



Fig. 3. Diastylis borealis. 



Fig. 3k. First pair of pereiopoda. 



Fig. 4. Nannastacus binoculoides (lateral view). 



Fig. 4". The same (dorsal view). 



