MONOGRAPH OF THE EXISTING CRINOIDS. 329 



Among the rnacrophrcate forms basal rays arc seldom developed. The}' are 

 found in the large species of PromachocrimiS (figs. 294, p. 263, and 505, p. 371), Helio- 

 metra (figs. 292, 293, p. 263, and 507, p. 371), and Solanometra (figs. 295, p. 263, and 

 506, p. 371), but they are usually more or less imperfectly formed, and may be quite 

 insignificant or entirely lacking. They are rather large in the only specimen of 

 Tlnjsanometra (fig. 285, p. 261), which I have been able to dissect. In Psatlnjrorm Ini 

 (figs. 208-213, p. 241, and 502, p. 369) and Zenometra (figs. 214-216, p. 241, and 558, 

 pi. 5), they are prominent externally, where they bridge over the subradial 

 clefts in the interradial angles; but in Psathyrometra everything except the distal 

 ends appears to have been resorbed, for they only extend inward a very short dis- 

 tance from the periphery of the calyx, there terminating abruptly, so that in a dorsal 

 view of the radial pentagon they appear merely as five small calcareous masses, one 

 in the outer part of each of the interradial areas. I found them to be rather well 

 developed in the single specimen of Coccometra hagenii (fig. 284, p. 261), which I 

 dissected, though they did not occur in the specimens dissected by Carpenter. 



They were not found in Pentametrocrinus japonicus (fig. 299, p. 264), P. varians, 

 Compsometra laveni (fig. 282, p. 261), HatJirometra prolixa, PI. tenella, H. dentata 

 (fig. 290, p. 262), Erythrometra ruler (fig. 288, p. 262), Trichometra aspera (fig. 291, 

 p. 262), T. vexator, Perometra diomedese (fig. 289, p. 262), or in Antedon (figs. 280, 

 281, 283, p. 261, and 593, pi. 15); nor were they evident in the specimens of the 

 oligophreate species Neometra multicolor (fig. 263, p. 257), Calometra separata, 

 Catoptometra Jiartlaubi (fig. 251, p. 253), Zygometra comata (fig. 252, p. 253), 

 Mariametra subcarinata (fig. 260, p. 255), Craspedometra acuticirra, Himeroinetra 

 martensi (fig. 254, p. 253), Pontiometra andersoni (fig. 261, p. 255), AmpJilmttra 

 pliiliberti (fig. 258, p. 255), or A. ensifer (fig. 256, p. 255), which I was able to examine. 

 As stated by Carpenter, they are not found in Leptometra (figs. 500, 501, p. 369). 



Large basal rays occur, just proximal to the extremely reduced and laminar 

 basals, in Atopocrinus (fig. 227, p. 245). 



Systematically the basal rays are of very uncertain value, and one must be 

 exceedingly cautious in drawing conclusions from their presence or absence. Among 

 the Comasteridse they are usually diagnostic enough to admit of the reference of a 

 specimen to that family upon the characters afforded by them, particularly the 

 more or less localized expansion; but in the other families any dependence upon 

 them is very hazardous, more so even than upon the characters furnished by the 

 rosette. They are occasionally valuable indices, for a specimen possessing them 

 will usually be found to belong to the Oligophreata, though this is by no means 

 always true. 



To state it broadly, basal rays are developed in all of the Comasteridse, and in 

 all of the Tropiometridse, in many of the Thalassometridre and Charitomctrida 1 , in 

 a few of the Himerometrida?, Mariametrida: , and ColobometridsB, and in half a dozen 

 or so of the macrophreate species, mostly large ones, and mainly those which show 

 an approach to the Oligophreata in other ways; in other words, they occur in such 

 species as possess radials nearly or quite horizontal in position, while they become 

 less and less evident as the radials take on a progressive upward slant. 



79146 Bull. 8215 22 



