Clark — Two New Crinoid Genera. 151 



scries. It therefore appears that, if Metacrinvs be deemed 

 worthy of generic rank, which no one has questioned, the two 

 divisions of the genus now known as Isocrinus are equally 

 entitled to generic rank, as they are as different from each other 

 as the /. asteria group is from Metacrinvs. 



The species of the Isocrinus asteria group are congeneric with 

 the fossil Isocrinus pendulus of von Meyer, which is the type of 

 Isocrinus of L. Agassiz, and several other genera have been 

 founded on other species of the same group. No generic name 

 has so far been given to any species of the J. parrse group, and 

 I propose to differentiate them from the /. asteria group under 

 the name Endoxocrinus. 



The peculiar species described by Dr. P. H. Carpenter as 

 Pentacrinus narcsianus differs in some important characters 

 both from Endoxocrinus and from the remaining species of 

 Isocrinus and appears to be worthy of rank as a separate genus. 



Endoxocrinus ^en. now 



Genotype. — Encrinus parrse Guerin, 1835 (= Pentacrinus mulleri 

 Orsted, 1856). 



A genus of Pentacrinitidse in which the first two post-radial joints are 

 united by syzygy, and the isotomous division series are all of two joints 

 united by syzygy (interpolated); the first oblique muscular articulation is 

 between the second and third brachials beyond the last axillary; infra- 

 basals always ( ?) absent, and interior ends of basals more or less resorbed, 

 the primary axial canals forking and entering the basals through two 

 apertures;* basals large and broad, forming, when viewed dorsally, a 

 rounded-pentagonal figure. 



Geographic Distribution. — Caribbean Sea and Gulf of Mexico; Atlantic 

 coasts of southern Europe and northern Africa (with the outlying 

 islands); East Indies; not known as a fossil. 



Depth .—84-1095 fathoms. 



The following species are included in this genus: 

 E. alternicirrus (P. H. Carpenter). 

 E. parrse ( Guerin). t 



* Reichensperger (Bull. Mus. Comp. Zool. Vol. XLVI, No. 10, p. 173, December, 1905) 

 figures the condition of the axial canals in Endoxocrinus parrse, misidentified as 

 Isocrinus {"Pentacrinus") decorus. The course of the canals in the latter species is 

 quite different. 



t This species, which inhabits the shallowest water of any of the genus, is extra- 

 ordinarily variable, while the others appear to be pretty constant in their characters; 

 this accords with the rule that a species of a genus which occupies a habitat on the 

 borders of the habitat of the genus as a whole, either geographically or bathyme- 

 trically, is more variable than are the other species of the same genus; thus Rhizocrinus 

 lofotensis and the corresponding species on the American coast are very commonly 



