CONTRIBUTIONS TO PALEONTOLOGY. 133 



ACTINOCRINUS CALYPSO ( n. s.). 



Body of medium size, somewhat narrowly turbinate to the bases of 

 the free arms. Basal plates proportionally large, with a somewhat 

 small column-facet. First radial plates of moderate size, with 

 upper and lower lateral margins subequal. Second radial s about 

 half as large as the first, hexagonal. Third radials much smaller , 

 pentagonal, the upper lateral angles slightly truncated; the upper 

 sloping sides each supporting a series of two small supraradial 

 plates : from the upper one of these rise two arms in the anterior 

 and antero-lateral rays, giving four arms to each of these rays. 

 The postero-lateral rays are probably the same, which would give 

 an arm-formula of 



4 



}I^ = 20 arms. 



First interradial plate intermediate in size to the first and second 

 radials, hexagonal; supporting two smaller hexagonal or hepta- 

 gonal plates in the second range, with a larger number of very 

 small plates above, meeting with those of the dome. Anal area 

 not determined. 



Arms round, slender, twice or twice and a half as long as the height 

 of the cup, composed of a double series of very short interlocking 

 plates, each of which bears a long tentacle composed of very long 

 joints. 



Surface of plates marked by low, distinct, rounded, radiating ridges, 

 from one to four at each margin, most numerous at the base and 

 decreasing upwards. A strong rounded ridge commences at the 

 upper margin of the first radial plate, and extends through the 

 middle of the ray to the base of the free arms, where it equals 

 them in size, and is longitudinally marked by granulose strise. 



This species differs from A cauliculus in the surface markings; while 

 the arm-formula, as well as the arm-structure, appear to be alike in both: 

 it also differs from that species in the form and relative height of the 

 basal plates. 



Geological formation and locality. In the shales of the Hamilton group: 

 in Western New- York. 



