Echinostrephus molare, &g. By C. Stewart. 911 



Pedicellarire. — The pedicellariae are very scantily present. The 

 gemmiform variety is remarkable for the complete absence of the 

 secondary solid fang found in Echinometra, Heterocentrotus, and 

 in some members of the genus Strongylocentrotus. There is a 

 slight bulging to the right, at the base of the teraiinal fang, but it 

 shows no trace of a spine. This feature is of interest, as the 

 terminal with one basal fang is held by M. E. Perrier to be 

 characteristic of the Echinometradae, to which family most would, 

 I should think, refer Parasalenia. The tridactyle form is exceed- 

 ingly delicate, and I was unable to obtain any perfect, nor could 

 I find any of the other varieties. 



The spicula of the ambulacral tubes are unlike any that I have 

 found in other JJesmosticha. They are biacerate, and generally 

 slightly bent in the centre. Their concave side is usually provided 

 with two often bifid spinules. It would be interesting to know 

 the structure of the viscera. Unfortunately my specimen was 

 thoroughly cleaned out and dry. 



Stomopneustes. — This genus is interesting as often showing con- 

 siderable varieties in the form of the corona, which, though usually 

 circular, is sometimes elliptical. It is remarkable also for the size 

 and structure of the spicula of its ambulacral tubes, the spicula 

 being equally well developed in a specimen of 1 inch diameter as 

 in one of 4. These alone suffice to determine the genus, but as 

 they have been already described and figured, I will not further 

 allude to them. 



Pedicellariae. — The ophiocephalous form is very abundant, and 

 they at once call attention from their large size. Their jaws are 

 more powerfully toothed than in any other genus I have examined, 

 but are most remarkable for being borne almost directly on the 

 calcareous stem. The muscular intervening portion, usually so 

 long, being in this case almost entirely absent, causes them to 

 resemble at first sight the gemmiform variety. Those of the 

 peristomal membrane are, however, of the ordinary character met 

 with in Echini generally. I was unable to find any gemmiform 

 pedicellariae, though I examined many specimens with great care. 



The tridactyle form is short, and varies greatly in size. They 

 are broad, and when the jaws are closed the whole length of their 

 finely serrate edges come in contact. The crest-like septum on the 

 inner surface of the bo.dy of the jaw is prolonged as an irregular 

 crest on the inner surface of the spoon-shaped prong of the jaw 

 nearly to its tip. The great variation in the size of these pedicel- 

 lariae, and tlie broad, spoou-shajied charat'tor of their jaws make the 

 smaller forms closely resemble the trifoliate variety, and lend 

 weight to Professor Agassiz's view, that the latter are rarely 

 stages of the former. But what I take hero to bo the trifoliato 

 form, although of the same dimensions as the smallest tridactylcs, 



3 p 2 



