146 



Bulletin, Vanderbilt Marine Museum, Vol. IV 



A B 



Text fig. 6. — Echinarachinus parma (Lamarck). A. Small bidentate gemmiform 

 pedicellaria, X 50. B. Bidentate tridactyl pedicellaria, X 50. 



are widest at the peristome and whieh about three-fifths the way to 

 the margin give off a prominent branch on each side, at about an 

 angle of 45° ; all three branches of each furrow extending to the 

 margin ; the median furrow sometimes is continued abactinally. The 

 peristome is quite small, the five calcareous teeth strong and very 

 sharp. The abactinal system is approximately central; there are four 

 genital pores. The anal aperture is situated abactinally in very young 

 specimens, marginal in many adults and actinal in very large, old 

 specimens. The primary spines are close-set, each with a disk-like 

 base forming a rim, the spine slenderer proximally than distally, 

 where it is swollen; the lateral surface is longitudinally verticillate. 

 The smaller spines are similar to the primaries but slenderer. 



The largest specimen of the series before me measures 76 mm. long 

 diameter, 74 mm. short diameter, 8.5 mm. vertical diameter, diameter 

 of abactinal system 7.5 mm., length of anterior petal 26 mm., length 

 of posterior petal 19 mm., length of spine at margin 1 mm., length 

 of spine at peristome 2.5 to 3 mm. 



The gemmiform pedicellariae are abundant on the specimens before 

 me, especially on the actinal surface each has a slender short stem, 

 slightly longer than the bud-like head, which is composed of two 

 elongated, tapered valves, each of which has a pointed hook distally; 

 the two valves forming a laterally compressed head. 



The ophicephalous pedicellariae are very abundant on both surfaces, 

 especially on the actinal. They are small, bivalve, laterally com- 

 pressed, short-stalked. 



