1886.] NATURAL SCIENCES OF PHILADELPHIA. 191 



Family XXV. CATILLOCRINID^ W. and Sp. 



The group of Crinoids for which we propose the name Catillo- 

 crinidfe consists only of the genera Catillocrinus and 3Iycocrinus, 

 which have been distinctly separated by all previous writers. 

 Catillocrinus, which was described by Meek and Worthen as 

 closely allied to Symbathocrinus, was referred by Zittel and De 

 Loriol to the Pisocrinidae, which we regard as a mere subdivision 

 of the S3^mbathocrinid8e. The form, when we include the arms, 

 is similarly cylindrical, the arms rest likewise directly upon the 

 first radials, and are composed of a single series of plates. Piso- 

 crinus even has irregular radials, which is so characteristic of 

 this family, but beyond that the two groups are quite distinct. 

 Mycocrinus, according to Schultze, forms a family by itself. He 

 took it to be a Crinoid without arms, which, in place of arms, he 

 thought had been provided along the ventral surface with numer- 

 ous ambulacral grooves. Zittel, and also De Loriol, have placed 

 Mycocrinus among the genera which were said to be imperfectly 

 known. 



In the Catillocrinidse, the calyx is composed of only two series 

 of plates, and these are most remarkable for their extremely irreg- 

 ular form and distribution. The radials are massive, especially 

 at the upper margins, where they are transversely truncated on 

 the same plane all round. The radial plates differ in form and 

 size. Those of the two antero-lateral raj^s, as a rule, are much 

 larger than the three others, but, while at their upper margin 

 they are from three to six times as wide as the others, all are at 

 the basi-radial suture about equal in width. The anterior, and 

 both postero-lateral rays, rarely possess more than one arm each, 

 but in the two antero-lateral ones the arms are always numerous. 

 Every arm articulates directly upon the truncate upper margin 

 of the radial without the aid of axillary pieces, and remains 

 simple from the base up. The arms are in contact all around the 

 calyx, and are composed of a single series of very similar pieces. 

 They connect with the inner cavity by a peculiar groove, which 

 follows the truncate upper face of the radials. This groove con- 

 tains the ambulacral canal and food passage, and there is under- 

 neath, separated by a solid partition, another groove, which near 

 the inner margin penetrates the plate, and takes a distinctly down- 

 ward course toward the inner cavity, which throughout this family 

 is exceedingly small. 



