428 



PROF. F. J. BELL ON THE TEMNOPLEURIDiB. [Juiie 1, 



1. Salmacis bicolor, Ag. 



Salmacis bicolor, Agassiz and Desor, Cat. Rais., Ann. Sc. Nat. 

 (3) vi. p. 359. 



This, when completely covered with spines, is a most beautiful 

 form : above the ambitus it is covered with short sharp purplish red 

 spines, banded with greenish-yellow ; at and below the ambitus the 

 spines are much stronger and longer and are more closely packed, 

 while the colours are reversed in relation, and they may be said to 

 be of a greenish-yellow, banded with a purplish red ; the base, 

 however, is always coloured red. Around the actiiiostome the spines 

 are still stronger and are completely flattened. The test is well 

 rounded and by no means conical. The actinal and abactinal arese are 

 of a moderate size ; a bare median space can, above the ambitus, be 

 distinctly made out in both the ambulacral and interambulactal areae. 



In the denuded test the primary tubercles on the interambulacral 

 plates are, above the ambitus, best developed on the half of the 

 plate nearest the ambidacral pores ; about the middle of the side of 

 the test there are two well developed primary tubercles, and inter- 

 nally to these there are two smaller ones ; passing upwards these 

 latter gradually diminish in size till they disappear ; and within a few 

 plates of the abactinal area the same happens with the outermost 

 row of tubercles ; so that the uppermost of the coronal plates have only 

 one well-developed primary tubercle each. At the ambitus there 

 are five well-developed primary tubercles on each interambulacral 

 plate ; and these tubercles, forming a close mail on the actinal face of 

 the test, gradually disappear as they pass towards the actinostome. 

 There is a fairly well-marked series of miliary tubercles running 

 along the upper edge of each coronal plate ; but these become much 

 more irregular on the uppermost plates. A dark-coloured band runs 

 along the sutures of the plates above the ambitus. 



On the ambulacral plates the primary tubercles form a single row, 

 which is placed quite at the outer edge and extends regularly from 

 pole to pole, gradually decreasing in size as they pass in either direction 

 from the region of the ambitus ; it is only quite close to the ambitus 

 that a second row of primary tubercles is at all well-developed. The 

 actinostome is of a moderate size, not sunken ; its decagonal form is 

 well marked, the ridges connecting the auricles are low ; the pore- 

 areas are wide, four pores, or two pairs, being placed in an almost 

 horizontal line. The sutural pores appear to become indistinct with 

 age. 



[8] 



