92 
PALEONTOLOGY OF NEW YORK. 
Subgenus ACTINOCONCHUS, McCoy. 1844. 
In the same work that contained the original description of Athyris, McCoy 
proposed the above term for a shell which he described as Actinoconchus 
paradoxus. 
“ General Characteristics. —Shell globose; the margin of both valves greatly 
extended, forming a flat, circular, striated disc; spiral appendages as in Athy- 
m.”—(Op. cU., p. 149.) 
Its affinities with Athyris were evident to the author, and later writers have 
regarded it simply as a synonym for that term. The Actinoconchus paradoxus 
was subsequently shown by Davidson to be the same shell as Phillips’ Spirifera 
{= Athyris) planosulcata (1836), which McCoy had himself identified among the 
Carboniferous fossils of Ireland from desquamated specimens (p. 148).* 
There seem to be excellent reasons for reinstating this term in its original 
application, as Athyris planosulcata is a strongly individualized species which 
may well serve as the type of a group. 
It is characterized by the extravagant development of the concentric lamel¬ 
lar expansions! which are striated radially by distant sulci “ about half a line 
apart” (Davidson). These expansions appear to be actually fine, tubular sp ines 
connected by, or imbedded in a tenuous calcareous plate. The interior of the 
pedicle-valve bears a median septum which traverses the pedicle-cavity and 
half the length of the shell; also two strong dental plates which are continued 
forward, slightly diverging, for more than one-half the length of the septum. 
Mr. Davidson has given elaborate illustrations of the spirals and loop of this 
species, from preparations by the Rev. Norman Glass,! and from them it appears 
that the latter organ, the loop, has essentially the same conformation as in 
Cliothyris pectinifera, though it is placed further forward (see Silurian Supple¬ 
ment, p. 98, fig. 1.). The saddle of the loop is neither divided nor pectinated, 
while the spiral ribbon bears short spinules “ on the edge and face of the lamellm 
fronting the sides of the shell ” (Davidson). Athyris planosulcata is a species 
* McCoy afterwards referred the species to the genus Athyius : British Palaeozoic Fossils, p. 436. 1855. 
t See Davidson’s superb figures in Carboniferous Brachiopoda, pi. xvi., figs. 7, 8. 
f Supplement to British Silurian Brachiopoda, p. 98, figs. 1, 2, pi. iv, figs. 14-19. 
