OP ARTS AND SCIENCES. 209 



Oystechinus vesica, A. Ag., nov. sp. 



This species is at once distinguished from its congeners by the flex- 

 ible nature of the test. This is so thin that its mere weight out of 

 alcohol is sufficient to change the shape of the test, which has, T^hen 

 seen in profile, much the appearance of an old felt hat. The outline 

 of the flat actinal surface is regularly elliptical. The anal system is 

 placed just beyond the edge of the ambitus ; the whole actinal surface 

 is more thickly covered by large primary tubercles than the abactinal 

 part of the test, where they are more distant ; the spines are short, 

 slender, sharp ; the color in alcohol is greenish brown. The most 

 prominent character of this species is the large size of the plates of 

 ambulacral area, resembling, in this respect, more Galerites than Anan- 

 chytes. — Station 153, 1,675 fathoms; Station 298, 2,225 fathoms. 



Homolampas fulva, A. Ag., nov. sp. 



The species on which this genus was originally established was quite 

 small ; it is therefore difficult to compare the two. Outline, seen from 

 above, is slightly heart-shaped, greatest width near anterior extremity 

 across abactinal system ; anterior ambulacrum broadly re-entering anal 

 extremity deeply indented. A few large tubercles in interambulacral 

 spaces carry long curved spines ; rest of test on abactinal side carries 

 short slender spines of uniform length, closely crowded together ; on 

 actinal side, posterior ambulacral areas bare ; actinal plastron and 

 lateral interambulacral spaces paved with large tubercles regularly 

 arranged and carrying moderately long curved spines ; subanal fasciole 

 broad, pentagonal in outline. Seen in profile, test slopes regularly 

 from apex, the short side anteriorly, the long side towards anal ex- 

 tremity, which is anteriorly truncated ; color in alcohol, yellowish. — 

 Station 271, 2,475 fathoms. 



Argopatagus vitreus, A. Ag., nov. gen. & sp. 



This genus is allied to Homolampas. It has, like it, a subanal fas- 

 ciole, but no lateral fasciole, a more labiate actinostome. The abac- 

 tinal surface is covered by distant primary tubercles of uniform size 

 both in ambulacral and interambulacral areas. They are more nu- 

 merous, but smaller, on the actinal surface. 



In this species the apex and apical system are posterior, the outline 



from above is elliptical, slightly re-entering anteriorly. The test is 



quite low ; actinal surface flat, regularly arching from apex to anterior 



and posterior extremities. The plates of the ambulacral and inter- 



vol. xiv. (n. s. vi.) 14 



