117 
SPIRIFER trigonalis. 
TAB. CCLXYV. 
Syn. Anomites trigonalis, Martin Petr. Derb. 
Tabl. 36, f. 1. 
Sp. Car. Gibbose, transversely striated; with 
26 radiating sulci ; hinge line as long as the 
shell is wide ; front semicircular ; the three 
central ridges elevated ; beaks incurved ap- 
proximated., 
EE 
Auruoven this is named trigonalis, the front is so 
round that it can hardly be called even obtusely angular; 
the spaces between the sulci are rounded ; three of them 
occupy the elevated part of the lesser or upper valve, 
and these are again obscurely divided, the central one into 
three and the others into two; the flat back meets the 
sides at anacute angle, it is striated ; the whole surface 
is regularly and finely striated transversely ; the striz 
are elevated and sharp, but often are worn down or ad- 
here to the stone the shell is imbedded in. 
The first specimen of this shell in which I discovered 
the internal spiral appendages was imbedded in a mass of 
Chert that was presented to me by the most eminent 
friend to science Sir J. Banks, upon whose estate at 
Overton near Ashover, Derbyshire, it was found in the 
Mountain Limestone ; I have confounded it with Anomia 
striata of Martin in my paper in the Linnean Transac- 
tions, vol. XII, part 2, p. 516. The shell is lined, and 
the spiral contents coated with minute crystals of 
Quartz. Within the last two years many specimens of 
