BRISSUS LATECARINATUS. 219 



a small tridentate occurs with valves .30-.35 mm. long, with entire margins. 

 As in the Mediterranean specimens, the large tridentate pedicellariae have 

 very conspicuous teeth on the margins of the valves. I found ophicephalous 

 pedicellariae only on one, and that a half-grown specimen. 



Brissus latecarinatus. 



Spatangus brissus var. latecarinatus, Leske, 1778. Add. ad Klein, p. xx, 185. 

 Brissus carinatus Gray, 1825. Ann. Phil., 26, p. 431. 



Plate 146, fig. 15. 



This is the Indo-Pacific species of the genus and its wide range extends as 

 far as Panama. It is true that Verrill described the Panamic species as obesus 

 and Mr. Agassiz accepted this third form of Brissus in the Revision. But he 

 clearly expresses doubt as to its validity, and I find myself unable to distinguish 

 specimens from Panama from those of the same size from various Pacific Islands 

 and even from Mauritius. Indeed, the characters of the fasciole and petals 

 mentioned in the Revision as distinguishing the Atlantic from the Pacific 

 species do not seem to be at all constant. 



The pedicellariae are in general similar to those of the Atlantic species. 

 Globiferous seem to be very rare but are usually present on or near the periproct; 

 the valves are about half a millimeter long and closely resemble those of brissus. 

 Rostrate pedicellariae, with valves like those of brissus, .60-.85 mm. long, are 

 more common. Large tridentate pedicellariae are present on the periproct 

 and on the ambulacra ventrally; the valves, which measure .37-1.75 mm., 

 have a lower, wider apophysis and much longer teeth on the margins of the 

 blade than in brissus; the marginal teeth may be one fifteenth of the length of 

 the valve. These large characteristic pedicellariae were practically wanting 

 on a small specimen but on the other hand, the small specimen had ophicepha- 

 lous pedicellariae, which were quite lacking in the large individual examined; 

 these pedicellariae are like those of brissus and the valves are about .20 mm. 

 long with a loop .05-. 10 mm. in addition. Besides the large tridentate pedicel- 

 lariae, there is a very characteristic form of tridentate found on both specimens, 

 near the mouth and on the posterior ambulacra just above the ambitus. In 

 this form, the valves (PL 146, fig. 15) .60-.80 mm. long, are slender, strongly 

 compressed, with very thick, slightly serrate margins. They are thus very 

 markedly different from the corresponding slender tridentate pedicellariae of 



