96 
PALEONTOLOGY OF NEW YORK. 
deeply bilobed, its anterior margin and the edges of the secondary volutions 
fimbriate. The precise value of this pectination of the 
saddle and coils it is difficult to determine; it appears 
to be developed differently in different individuals. We 
are not satisfied as to the existence of this character in 
A. trinucha and A. subquadrata, but in A. Dawsoni it is 
absent. Some individuals give indication of the pectina¬ 
tion of the stem and the accessory lamellaB of the loop, 
and it has been shown by Zugmayer that in Athyris 
(Spii'igera) oxycolpus, Emmrich, of the Rhaetic beds, the 
accessory lamellae are deeply serrated, a feature coexist¬ 
ing with a bilobed saddle.* 
In A. subquadrata the lateral branches of the loop are long-and projected for¬ 
ward at a sharp angle. In A. trinuclea, the origin of the loop is more anterior, 
the lateral branches erect and high, the surface of the bilobed saddle being 
close under the opposite side of the coils. Athyris Dawsoni is a very interesting 
Fig. 68. 
Pectinated loop of Athyris 
oxycolpus, Emmrich. 
(Zugmayer.) 
Fig. 69. Fig. 70. Fig. 71. 
The loop of Athyris {Seminula) Dawsoni, sp. nov.; showing the variation in development of the saddle in different 
individuals. Fig. 70 is a view from the umbonal region of the specimen represented in Fig. 69, indicating the 
marginal position of the accessory lamellae upon the umbonal blades. (c.) 
form occurring with most beautiful and exceptional preservation, the brachi- 
dium being retained with the slightest incrustation of calcareous matter upon 
it; all the rest of the shell and the filling of its interior cavity being removed. 
In this species the loop is normally almost without a saddle; at the union of 
the lateral branches there is a slight forward protuberance on each side, the 
stem arising therefrom almost without angulation ; the accessory lamellae, as 
shown in the accompanying figures, lie upon the inner edges of the primary 
* Zugmayer, Untersuchungen ueber rhaetische Brachiopotlen ; Beitraege zur Palseontologie CEsterreich- 
Ungarns nnd des Orients, pi. iii, figs. 21-23, and p. 353, figs. 1-3. 1882. 
