Correspondence. 131 
sulci," and "these expansions appear to be tine, tubular spines connected 
by, or imbedded in a tenuous calcareous plate'* (A.planosulcata), while 
Seminula has a smooth exterior (A. subtilita). 
The most primitive athyroid known is Terebratula Iceviuscula Sow- 
erby, of the English Wenlock. the brachial apparatus of which was 
first demonstrated by Glass to be structurally different from that of 
Athyris, and this species now serves as the type of Olassina, gen. nov. 
Betzia, King, is shown to possess a very peculiar and unexpected in- 
terior structure, which at present is not known to be common to any 
other species. The many American retzioid forms are here shown to 
belong to Bhynchospira, Hall; Homceospira, sub. gen. nov. (type B. 
evaxHall); Ptychospira, gen nov. (type Terebratula ferita vonBuch); 
Eumetria, Hall; Acambona, White; Hustedia, gen. nov. (type Terebrat- 
ula mormoni Marcou); Trematospira, Hall; and Parazyga, gen. nov. 
(type Trematospira hirsuta Hall). 
Uneltes is placed with the retzioid genera, but the nature of the pri- 
mary lamella? at their junction with the crura seems to forbid this ar- 
rangement, and the family Spiriferidui is suggested by the writer as a 
more suitable place; Uncinella, Waagen, also might remain where its 
author provisionally placed it, and Uncites in the subfamily Uncitince. 
The genus Anoplotheca, Sandberger, heretofore little understood, 
proves, in its known characters, to be congeneric with Bifida, David- 
son, and Ccelospira, Hall. "The structure of the loop is still unknown" 
in the type species of Anoplotheca, and Hall and Clarke state that 
"with our present knowledge it seems necessary to conclude that the 
term Bifida is altogether synonymous with Anoplotheca" (p. 133), in 
which case it may be assumed that the loop of the latter genus will, 
when known, prove to be structurally identical with that of Bifida as 
worked out by Clarke. Leptocozlia, Hall, which was thought to be a 
terebratuloid, proves to be a spire-bearer. The structure of its spirals 
and loop are not yet fully known. From 'Ccelospira concava, L.fiabel- 
lites, the type species "differs, as far as its structure is known, only in 
its greater size and coarser, simple plication of the surface. In general 
contour, structure of hinge, cardinal process, muscular scars and inter- 
nal septa it agrees throughout with Anoplotheca and Ccelospira." In 
regard to the latter "it is clearly evident that the structure in the spe- 
cies of Ccelospira is essentially the same as in Anoplotheca venusta, and 
A. (Bifida) lepida." For the present, it seems better to merge these 
unestablished genera into one, Anoplotheca, until they can be shown to 
have a biologic significance. 
Vitulina, Hall, also proves to be a spire-bearer and "now takes its 
place quite naturally in close association with Ccelospira and LeptocOB- 
Ha:" Anabaia, Clarke, gen. nov., "appears to be the precursor of the 
Devonian shells referred to Anoplotheca and Leptocozlia" 
( \//rlospira, gen. nov., is based upon Orthis bisculata Emmons. It is 
■ difficult at present to indicate with any degree of exactness the relation 
which this genus bears toother spire-bearers. However, the nature of 
ithe primary lamella' and of the incomplete loop point to the Spirifer- 
