188 Bulletin Vanderbilt Marine Museum, Vol. VII 



The larger specimen differs from the smaller one only in size 

 and in the fact that the bivium is less distinctly defined, the dorsal 

 papillae being quite small, fugitive and more difficult to locate 

 in the alcoholic specimen. 



The body-wall, a uniform chalky-white in the preserved speci- 

 men, gives no hint of the original color. It is unusually tough, 

 leathery, brittle with calcareous deposits, and is composed of 

 two distinct layers, the outer one being a practically continuous 

 pavement, consisting of delicate, thin, calcareous scales, the ma- 

 jority being of a hexagonal pattern and some of irregular denticu- 

 lar shape crowded between ; each scale consists of small, irregular 

 calcareous coalescent bodies with minute interstices between, 

 (forming a pattern of continuous irregular reticulation ; the scale 

 is highly porous. 



The inner wall is composed of numerous much coarser cal- 

 careous bodies of various shapes, which, however, are of three 

 principal types : (a) clavate both perforate and non-perforated, 

 rodlike, composed of four transversely banded lobes ; (b) circular 

 and oval disks, variously perforate with from one to twelve holes ; 

 (c) numerous small crescents and double-curved crescent-like 

 bodies; (d) small crosses with equal arms, less frequently a sort 

 of double-cross with six short equal arms divergent. There are 

 also occasional long, convolute, needle-like spicules with one or 

 both distal ends bent or curved. The above described varieties of 

 spicules were dissected from the median ventral surface near the 

 intermediate ambulacrum of the trivium, 



A piece of tissue snipped from the median dorsal surface, when 

 dissected, shows no disks present, but there is an intricately inter- 

 meshed spicule formation, comprised of three principal types of 

 long, needle-like spicules ; (a) straight spicules with a bifurcate, 

 acuminate apex on one end and a single needle-point on the 

 opposite end; (b) bow-shaped spicules with the subdistal bend 

 of both apical portions, and (c) needle-thin, elongate spicules, 

 tri- or quadri- sinuate with both apices curved. There are also a 

 few anchor spicules which have six slender, somewhat unequal, 

 curved and twisted prongs, forming an irregularly six-pointed 

 star in one plane, with a seventh branch arising from the center 

 of this and extending at right angles therefrom, the distal portion 

 of this branch bent obliquely outward. Less numerous but defi- 



