.924 
MR, P, H. CARPENTER ON A NEW 
separate the radials. Except on the anal side, these primary interradial plates of 
Thaumatocrinus end simply in a free rounded edge at the margin of the disc (Plate 71, 
figs. 1-3, 5, i), which is doubtless due to the simplicity of the arms; for these become 
free almost at once, and are not connected laterally by much perisome, in which 
higher orders of interradials could be supported. But in the presence of the appendage 
on the azygous interradial (Plate 71, figs. 2, 4, 5, act), Thaumatocrinus bears a re¬ 
markable resemblance to Reteocrinus. The latter genus was established by Billings 
on some badly preserved fragments from the Trenton limestone of Ottawa.* * * § Meek, 
and Wetherby have since described some species of Glyptocrinus presentiug very 
similar characters to those of Billings’ genus, and have noted the resemblance 
between them; while Wetherby! subsequently came to the conclusion “that several 
forms of our so-called Glyptocrinus should be referred to this genus.” Wachsmtjth 
and Springer | have accordingly reconstructed Reteocrinus, and have proposed as 
type of the genus Glyptocrinus nealli (Hall), a proceeding for which they have been 
severely criticised by Miller. § 
The original examples of Billings’ type species were so imperfectly preserved, that 
the distinctive characters of his genus were incompletely known. As, however, 
Wachsmuth and Springer, like Wetherby, fully believed Glyptocrinus nealli to be 
a Reteocrinus, I do not see how they could have redefined the genus better than by 
selecting such a well-known species as their type. 
Taking Reteocrinus then as defined by Wachsmuth and Springer, we find that its 
posterior interradial area is wider than the other four, “with a conspicuous row of 
decidedly larger and more prominent special anal plates along the median part.” 
Billings gives a good figure of this structure in R. stellaris, || and speaks of it as 
follows: “If this series of joints constitute a true arm, then there must he six arms 
in this species.” The same feature appears, though less prominently, in R, nealli 
(Hall) sp., and in R. haeri (Meek) sp., and also in R. richarclsoni (Wetherby), 
though in R. gracilis (Wetherby) and II. cognatus (Miller) sp., it appears to be 
absent. It is unusually distinct, however, in Xenocrinus penicillus (Miller)!! 
(Plate 71, fig. 8), a type which closely resembles Reteocrinus in general appearance; 
and I fully agree with Messrs. Wachsmuth and Springer** in thinking that it should 
* ‘ Canadian Organic Remains.’ Decade iv., p. 63„ 
f “ Description of new Fossils from tlie Lower Silurian and Subcarboniferous Rocks of Ohio and 
Kentucky.” Journ. Cincinnati Soc. Nat. Hist., vol. iv., April, 1881, p. 7 (of separate copy). 
X Revision. II., p. 191. 
§ “ Description of Two New Genera and Eight New Species of Fossils from the Hudson River Group.” 
Journ. Cincinnati Soc. Nat. Hist., vol. v., April, 1882, pp. 12, 13 (of separate copy). 
|| Op. cit., p. 64, pi. 9, fig. 4a. 
'• Description of Some New and Remarkable Crinoids and other Fossils of the Hudson River Group, 
and notice of Strotocrinus bloomfieldensis." Journ. Cincinnati Soc. Nat. Hist., vol. iv., April, 1881, 
pi. 1, fig. 3, and pi. 4, fig. 4, pp. 71-73. 
** Revision. IT., p. 185. 
