MONOGRAPH OF THE EXISTING CRINOIDS. 329 



Among the macroi)hreate forms basal rays are seldom developed. They are 

 found in the large species of Prnmachocrirms (figs. 294, p. 263, and 50.5, p. .371), Ilelio- 

 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 specmien of 

 Thysanometra (fig. 285, p. 261), which I have been able to di.ssect. InPsathjrometra 

 (figs. 208-213, p. 241, and 502, p. 369) and Zenametra (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 everytiiing except the dLstid 

 ends appears to have been rcsorbed, for they only extend mward a very short dis- 

 tance from the periphery of the calyx, there terminatuig 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 intciTadial areas. I found them to be rather well 

 developed m 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 Pentametrocr'mus japonicus (fig. 299, p. 264), P. varians, 

 Compsametra loveni (fig. 282, p. 261), Hailirometra proliia, H. tenella, U. dentata 

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

 p. 262), T. vexator, Perometra diomedex (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 kartlauhi (fig. 251, p. 253), Zygometra comata (fig. 252, p. 253), 

 Mariametra suhcarinata (fig. 260, p. 255), Craspedometra acutidrra, Himerometra 

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

 philiberti (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). 



Systematical^ the basal rays are of verj' uncertain value, and one must be 

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

 the Comasteridae 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 fui'nLshed by the 

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

 wall 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 Comasteridae, and in 

 all of the Tropiometrid;^, in many of the Thalassometrithw and Charitometri(la>, in 

 a few of the Himerometridse, ilariametridw, and Colobometrida\ and in half a ilozen 

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

 an approach to the OUgophreata 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. 82—15 22 



