Talbot — New Yor~k Ilelderbergian Crinoids. 29 



few specimens could the plates be distinguished. It also 

 seemed that there were two species, the fossils differing so 

 much in size, gibbosity and general appearance ; but further 

 study failed to reveal any real differences. Some of the forms 

 have a hemispherical calyx, and arms only three or four times 

 as long as the cup, while others have a flat cup and arms five 

 or six times as long ; and yet the plates of the calyx, the joints 

 of the arms, the pinnules and the cirri seem to be the same in 

 the two varieties. 



In the material from North Litchfield, the lower bed has 

 much the larger forms, all of which are compressed. The 

 upper bed has an abundance of the 

 smaller ones, a few of which have the 

 calyx gibbous, not flattened. The speci- 

 mens from Jerusalem Hill are uncom- 

 pressed and small. Wachsmuth and 

 Springer consider C. parvus the young 

 of C. plumosus; and it may be that it 

 was these small, uncompressed specimens 

 from the upper crinoid bed that Hall 

 had under observation when he described 

 the former species. If this assumption 

 can be proved, it may be well to regard m , „ _ . _ 



^ r • i. £ sv ■ i - Text-figure 3. — Anal sac 



6. parvus as a variety of 0. plumosus, of cordyiocrinus piumo- 



as these small forms occur at a slightly sus. a, right postero-lat- 



hiffker geological horizon. eral radial; b, leftpostero- 



xn ° , °j r .1 • j.1 lateral radial: c, first of 



From a study of the specimens in the anal serie8 of ^ lat ' es x 4 

 1 ale University Museum, the following 



new data may be given : In no case does the length of the 

 column exceed once and a quarter that of the crown, which 

 varies from 5 mm to 32 mm . A large majority of those speci- 

 mens which retain the column have very many unusually long 

 cirri. 



Several of the specimens have a feature which Bather states 

 is found in some of the Camerata, and which he explains as 

 being due to the fusing of the joints of the arms.* In these 

 forms the arms are composed of long joints, seemingly single, 

 with the upper and lower surfaces parallel and horizontal. In 

 parts of the arm, every other joint bears two pinnules on the 

 same side of the ray. This alternation of one- and two-pinnuled 

 joints does not extend throughout the whole length of the ray, 

 but in places it is every third joint that has this peculiarity. 

 Toward the base the joints are normal, that is, one-pinnuled. 

 In his description, Hall mentions the fact that some of the 

 joints have two pinnules ; but in his figure, f he represents most 



* A Treatise on Zoology, Pt. III. The Echinoderma, p. 116, 1900. 

 f Nat. Hist. N. Y., Pal., vol. iii, pi. 4, fig. 4, 1859. 



