NATURAL SCIENCES OF PHILADELPHIA. 309 



same form as the corresponding pieces of the other raj's described. 

 (Other rays unknown.) Arms very long, slender, and bifurcating 

 at least four times at irregular distances above the first divisions 

 of the raj^s ; pieces of the lower divisions generally longer than 

 wide, rounded and constricted in the middle, and expanded at the 

 ends ; while those of the smaller terminal divisions are usually 

 from three to four or five times as long as wide, and scarcely ex- 

 panded at the ends. Surface smooth. Finnulse not seen. 



First anal piece small, about as long as wide, and, as usual, 

 resting between the superior sloping sides of the first radial on 

 the left, and the second on the right, and bearing three or more 

 others, in direct succession above, that doubtless form a part of 

 the walls of the ventral extension. 



Column small, distinctly pentagonal near the base, where it is 

 composed of alternately thin and slightly thicker pieces. 



Length of body, to top of the larger radial pieces forming a 

 part of its walls, 0.14 inch; breadth, about 0.12 inch; length of 

 rays and arms above the bod}', 1 inch ; thickness of column near 

 base, about O.OT inch. 



At the same time that I propose to name and describe this deli- 

 cate little Crinoid as a new species, I suspect that it may not be 

 distinct from H. exilis of Hall, which has not yet been illustrated, 

 and has, unfortunately^, been only briefly described. If Prof. 

 Hall's description is strictly accurate, however, in several impor- 

 tant characters, the form under consideration must be clearly 

 distinct, as he states that the posterior lateral rays of H. exilis 

 bifurcate on the second pieces, and the anterior lateral on the 

 fourth; while, in the form here described, one of the posterior 

 lateral ra^-s bifurcates first on the Jifth piece, and the other on 

 the eighth; and, in the only one of its anterior lateral rays seen, 

 the first division takes place on the sixth or seventh piece. He 

 also says that the arms of H. exilis bifurcate once or twice, while 

 in our t^'pe they bifurcate at least four times above the primary 

 division of each ray. Again, he describes the bod}'' plates of if. 

 exilis as having the general curve of the body; but in our tj'pe 

 the subradial plates are so flattened as to impart a pentagonal 

 form to the lower part of the bod}'. 



This species will be at once distinguished from H. simplex, by 

 its frequently bifurcating arms and other well-marked characters. 

 From H. heterodactylus, which also has its arms several times 



18T2.] PART TIL— 21 



