GENESSEE SLATE AND CHEMUNG GROUP. 159 



third radials in double series, one above the other, on each sloping face, 

 the upper ones being short, broad plates, and support a third set, which 

 appear to have been more properly the first arm plates, although they 

 are all more or less broken in the specimen, so that it is impossible to 

 determine fully their true nature. The inner margins of these, and also 

 of the second range of supraradials, are closely pressed together, so as to 

 unite the cicatrices of the two upper plates, on which the arms rest, to- 

 gether forming only a single scar. Interradial areas large, four of them 

 similar in size, but varying in the arrangement of the plates. The first 

 plate in each of these areas is somewhat regularly hexagonal, the height 

 and width being about equal, supporting two smaller plates in the sec- 

 ond range, some of which are hexagonal, and others heptagonal; the 

 third range consists of three plates, above which they are not regular, 

 some having three, others four, and in one area there are five plates in 

 this range ; above this point they are more properly dome than inter- 

 radial plates. The fifth area, which corresponds to the anal area of the 

 unsymmetrical crinoids, is larger than the other four. The first plate 

 is large, equal in size to the largest of the first radials, and heptagonal 

 in form, supporting three plates in the second range in the form of an 

 arch, with four in each of the two next ranges, each range having the 

 same arcuate feature, which feature continues, though with less distinct- 

 ness, to near the base of the proboscis. 



The surface of all the plates of the calyx are very depressed convex, 

 with slightly concave centers, and more abruptly rounding near the 

 margins; or they may be described as flattened, with the margins 

 roundly beveled, the suture lines presenting the appearance of being 

 widely grooved. The plates of the dome are moderately convex, with 

 very distinct sutures. The plates of the calyx are marked over their 

 entire surface, except the most depressed part of the suture grooves, by 

 a system of small confluent granules arranged in concentric circles. 

 Those of the dome are simply finely granulose. 



Associated with the body described are several pieces of columns, of 

 rather less than a fourth of an inch in diameter, composed in some cases 

 of alternating larger and smaller discs, in others of similar sized plates, 

 all having their exterior surfaces longitudinally marked similar to the 

 plates of the body; also, a fragment of an arm, which is very thick and 

 strong in its habit of growth, and is supposed to be an arm of this 

 species, as there ,is no other form of arm, or of body, found associated 

 with them. The arm is broad and flattened, almost depressed along 

 the center of the back, and is composed of a double series of very short 

 plates, interlocking with each other along the center, but scarcely alteag 



