CLYPEASTER SUBDEPRESSUS. 307 



greatly; the poriferous zone is narrow; tlie tubercles are small, uniform 

 over the upper part of test ; the miliaries are large, so that granulation 

 appears quite homogeneous, the same granulation extending over the mad- 

 reporic body. The spines over the whole of test are fine, short ; the same 

 generally on the lower surface, where, although the tubercles are slightly 

 larger than on upper part of test, it is only immediately round the cavity 

 where the mouth is placed that we find larger tubercles carrying longer 

 spines. The ambulacra] furrows are well marked from edge of test to 

 actinostome, extending along the upper part of the test in the median 

 and lateral sutures to the extremity of the rosette. The small anal system 

 is at a short distance from the edge of the test on the lower side. 



The color is yellowish-green from above, — when alive, somewhat lighter 

 on lower side, where the sutures of the plates are a brilliant yellow, — the 

 poriferous zone is a dark carmine, the edge of the test and the internal part 

 of each plate of upper part of test is pinkish, surrounded by a yellowish 

 border. The height of the test varies extremely; we find all possible 

 stages between a highly arched test where ambulacral petals are placed, 

 suddenly tapering, and a thin edge scarcely rising towards apex, so that the 

 general aspect is that of an extremely flat Laganum when cursorily ex- 

 amined. A similar form of Clypeaster humilis is represented in the Pacific 

 Ocean by the Scutella latissima of Lamarck, which is nothing but an ex- 

 tremely attenuated Clypeaster humilis. Agassiz distinctly says it is allied 

 to C. scutiformis. This is an error, as it undoubtedly is a flat Clypeaster 

 humile, although by mistake it was subsequently referred to Laganum in 

 the Catalogue Eaisonne. The variations in our common species are figured 

 in the Plates ; a specimen figured on PL XII'. f. 4. is the young of the 

 flat type, while on PL XIII. f. 10 -IS we have the young of the speci- 

 men with a thick swollen edge, high central test, to which I had given in 

 the Preliminary Report the name of S. Ravenelli. A remarkably fine series 

 of this form from Georgia, in the Museum of Liverpool, shows that the char- 

 acters upon which I had distinguished it from C. subdepressus are only of 

 secondary importance. The internal structure of edge of test is of course 

 very different in the specimens with a thin edge or a swollen margin ; in 

 one case the pillars are few and broad, in the other they form quite a 

 series of concentric lamellae over a good portion of the interior of the test 

 {PL XII'. f. 4). 



The presence of a true Laganum in the West Indies has been often men- 



