TOXOPNEUSTES SEMITUBERCULATUS. 409 



Panama ; Feejee Islands ; Mauritius ; East India Islands. 



Toxopneustes semituberculatus 



! Echinus semituberculatus Vai... 1846, in Ag. Des. C. R. Ann. Sc. Nat, VI. 

 ! Toxopneusles semituberculatus A. Ag., 1872, Rev. Ech., Pt. I. p. 168. 



The principal characters which at once distinguish this species from its 

 West Indian representative (T. variegatus) are the comparatively much 

 larger actinostome, the large coarse granulation occupying nearly the whole 

 of the bare median interambulacral and ambulacral spaces, and the com- 

 paratively small size of the primary tubercles, as the larger number of coronal 

 plates in specimens of the two species of the same size readily shows. In the 

 abactinal system the genital openings are close to the apex, at the very 

 tip of the genital plates, indenting the extremity of the genital plate itself. 

 The aetinal cuts are broader, and the abactinal system larger than in T. 

 variegatus. In dried specimens the color of the test is of an olive-green," 

 with brighter bands along the poriferous zone. The buccal membrane is 

 plated, but not so thickly packed as in T. variegatus. The spines are com- 

 paratively shorter and more slender, of the general color of the test, only 

 somewhat darker. 



Galapagos ; Central Pacific America ; Cape St. Lucas. 



Verrill has described as Psammechinus pictus a young sea-urchin wdiich I 

 had, from analogy with the corresponding stages of Toxopneustes variegatus, 

 referred to this species. Mr. Verrill subsequently considered it to be the 

 young of (Boletia picta) Boletia rosea. I am still inclined, from want of better 

 proofs, to retain my view of the affinities of this small Echinus, especially 

 since I have had occasion to compare it with the young of Boletia pileolus 

 from the Sandwich Islands. The structure of the buccal membrane of Psam- 

 mechinus pictus seems, as far as we know anything of the young stages of 



