240 CATALOGUE OF THE BLASTOIDEA. 



remove these from Granatocrinus, and group them in a separate subsection under 

 another name " l . The first actual description of Granatocrinus to appear was that 

 published in 1866 by Messrs. Meek and Worthen, who appended many valuable 

 anatomical details, and discussed the affinities of this type to E/ceacrinus and to 

 Pentremites. Since that date their definition of the genus has been pretty gene- 

 rally accepted, but in 1882 we suggested certain modifications, which will be more 

 advantageously discussed farther on. 



Remarks. The majority of American palaeontologists having agreed to distinguish 

 as a separate genus a series of forms with the general structure of Pentremites Nor- 

 wood!, O. & S., P. melo, 0. & S., and P. Sayi, Shumard, under the name of Grana- 

 tocrinus, it became necessary to seek a well-defined type. Troost's G. cidariformis 

 never became more than an MS. name ; and, according to Dr. Shumard, the species is 

 identical with Pentremites granulatus, Roemer. The latter unfortunately is equally 

 little known, having been described only from an internal cast, no mention being made 

 of the structure of the summit. A knowledge of this being indispensable for a due 

 appreciation of the generic characters, we have therefore been obliged to seek 

 another type ; and we believe that this may be most readily found in Pentremites 

 Norivoodi, O. & S., not only from its general acceptance as a typical Granatocrinus, 

 but because it was one of the species first referred to this genus by American 

 palaeontologists. 



The description of Granatocrinus given by Meek and Worthen 2 was supplemented 

 by the following remarks : — "The generic formula of this group is exactly the same 

 as that of Pentremites, Say, so far as regards the number and arrangement of the 

 pieces forming the body, though the form and proportions of these pieces are so unlike 

 as to give a very different outline and general physiognomy to the entire fossil. They 

 are therefore readily distinguished from Say's genus, as properly restricted, by the 

 irregular oval, elliptical, or subglobose form, concave or less protuberant base, and 

 much narrower and more elongated pseudoambulacral areas, which extend the entire 

 length of the body, so as to give it more the appearance of an Echinoid. They like- 

 wise present differences in the arrangement of the ovarian (?) openings of the summit, 

 which are more intimately connected with the interradial pieces, being sometimes 

 excavated one into each lateral margin of these pieces (G. Sayi), or in other instances 

 piercing directly through them, so that each pair appears externally as a single open- 

 ing ((?. melo and G. Norwoodi), though they divide into two distinct canals before 

 passing entirely through the plates. The typical forms of this genus also have the 

 interradial pieces proportionately much larger than in the true Pentremites, though 

 tl lis is not a constant character." 



On a comparison of the species thus separated from Pentremites and united under 



1 A suggestion which wc have, to a certain extent, adopted by establishing our genus Cryptublastus, 

 i Kcport Gcol. Survey Illinois, 1866, vol. ii. p. 274. 



