TRIGONOCIDARIS. 471 



TRIGONOCIDARIS. 



Trigonocidaris A. Agass., 18G9, Bull. M. C. Z., I. 

 (See Part II. p. 289.) 



Trigonocidaris albida 



! Trigonocidaris albida A. Agass., 1869, Bull. M. C. Z., I. 

 (See Part II. p. 289.) 



PI. IV. f. 1-7 ; PI XXXVI. f. is. 



Straits of Florida. 



SALMACIS. 



Salmacis Agass., 1841, Val., Anat. Genre Eeh. 



Test moderately thick, more or less conical ; pores trigeminate ; tubercles 

 crenulated, not perforate, arranged in several vertical rows, at the same time 

 forming regular horizontal rows. Median interambulacral spaces frequently 

 bare; angular pores at junction of plates; abactinal system prominent; 

 actinal system small, with slight indentations ; spines fine, slender, longitu- 

 dinally striated, short. 



The auricles are often very high, thin, with high connecting ridges and 

 small auricular foramen. Ambulacral system broad. 



The different species of Salmacis are poorly represented in museums, 

 and with very few exceptions the specimens are mere tests without spines 

 and devoid of actinal membrane ; but few specimens exist from which any- 

 thing can be learned regarding the changes due to growth. The outline 

 of the test of all the species varies greatly, and the specific characters thus 

 far noticed are of course subject to doubt, owing to the comparatively lim- 

 ited material at our command. 



Salmacis bicolor 



! Salmacis bicolor Agass., 1841, Val., Anat. Genre Ech. 



PI. VHP.f. 11-12. 



Test moderately thick ; actinostome of moderate size, decagonal, with 

 very slight indentations. Abactinal system large, with broad genital rings ; 



