Verrill, N'otes on Madiata. 317 



(in the ratio of 16 to 15) diverging at a smaller angle than in 

 B. Scillw. In a side view the anterior end has a regularly convex 

 outline to the abactinal area, which forms a slight depression, from 

 thence the outline rises gradually to a point about half w^ay to the 

 posterior end and then curves rapidly downward to the truncate anal 

 region, which makes more than a right angle with the lower surface. 

 Subanal region obtuse, high and inflated, very convex ; posterior 

 median region of the '''•plastron'''' inflated, rising into a prominent 

 point. The sub-anal fasciole is broad, transversely reniform, its longi- 

 tudinal diameter to its breadth as 1:3. The " plastron " is shield- 

 shaped, rather broad, a little narrowed posteriorly, its length to 

 breadth of posterior end as 12 : 7. Color of test, in alcohol, uni- 

 form yellowish gray ; of spines, dark gray. 



Gulf of California, — E. Samuels (Coll. Boston Soc. Nat. Hist, and 

 Museum Yale College) ; Cape St. Lucas, — J. Xantus (Coll. Smiths. 

 Institution). 



This species is more liable to be confovxnded with ]3. Scilloe Ag. 

 than with any otlier known to me. It may be distinguished readily, 

 however, by its evenly rounded outline between the anterior margin 

 and ovarial plates ; by its more swollen posterior region, which is 

 due both to the elevation of the posterior interambulacrum and the 

 increased convexity, of the sub-anal and ventral areas ; by the less 

 anterior position of the abactinal areas ; by the relatively shorter and 

 broader plastron and sub-anal fasciole ; and by the latter being 

 placed rather upon the posterior than upon the lower surface, while 

 in B. ScillcB it is more nearly continuous with the plastron. 



Mcoma nigra Verriu. 



Kleinia (Ryssohrissus) nigra A. Agassiz, Bulletin M. C. Z., p. 27, 1863. 



This large species is closely allied to 31. grandis Gray, from 

 Australia. 



Length four inches ; breadth 3*6 ; height 1*9 ; length of anterior lat. 

 eral ambulacra 1-9 ; of posterior 2 ; length of anal area "7 ; breadth '45. 



Its outline is broad ovate, somewhat cordate anteriorly, and trun- 

 cate and slightly emarginate posteriorly. The upper surface is rather 

 depressed, but not flattened, covered with scattered larger tubercles 

 and A' ery numerous small ones. The tubercles are largest within the 

 peripetalous fasciole and beyond it on the posterior interambulacrum. 

 The anterior ambulacral area is but little sunken, with rudimentary 

 pores. The anterior-lateral ones are rather broad and deep, curving 

 forward, especially at the ends. The two posterior are somewhat 



