OP ARTS AND SCIENCES. 207 



as well as their similarity, in many respects, to such cretaceous forms 

 as Holaster, Cardiaster, and Ananchytes. j 



The present genus has a thin test, an outline from above resembling 

 Holaster, but when seen in profile a well-developed actinal anal snout 

 shows its affinity to the Pourtalesiee. Seen in profile, the outline is 

 regularly arched until it reaches the posterior extremity, which is 

 pointed, projecting above the anal snout. This genus has a short but 

 deeply sunken actinal groove and a small anal pouch. The color of 

 the test of this species is pinkish, sparsely covered on the abactinal 

 side by slender sharp spines of a uniform length. On the actinal side 

 the spines are larger. — Station 157, 1,950 fathoms; Station 147, 

 1,600 fathoms. 



Urechinus naresianus, A. Ag., nov. gen. & sp. 



Urechinus and Cystechinus have not the sunken actinal groove 

 which characterizes the Pourtalesias. In these genera the actinos- 

 tome is more or less central, and does not differ materially in its 

 structure or position from that of the more normal Spatangoids. The 

 structure of the ambulacra, however, is, as in Pourtalesias and the 

 other deep-water forms allied to them, quite different from that of the 

 Spatangoids, with which externally they present many points of re- 

 semblance. Urechinus in outline and general appearance resembles, 

 at first glance, Neolampas, but in the structure of the test it is more 

 closely allied to Cystechinus, having like it a nearly flat actinostome 

 and large ambulacral plates. The anal system alone recalls Neolampas 

 by its position in a shallow groove placed above the ambitus. The 

 young specimens differ but little from the older stages, the interambu- 

 lacral projection over the anal system alone is not quite so prominent, 

 and the actinostome less sunken. The number of primary tubercles 

 in younger stages is limited to one for each plate, only becoming 

 more numerous in older specimens when the whole test is thickly 

 covered with fine slendar miliary and secondary spines. The spines 

 are yellowish white, the test of a reddish brown color or pinkish color. 

 The lower surface of the test closely tuberculated. — Station 147, 

 1,600 fathoms; Station 146, 1,375 fathoms; Station 158, 1,800 

 fathoms. 



Cystechinus, A. Ag., nov. gen. 



This genus has the general appearance of Ananchytes, with the 

 simple ambulacral system of the Pourtalesias ; actinostome much less 

 labiate than in that group of Spatangoids. This genus and Urechi- 



