2 | Prof. W. King on Spiriter cuspidatus. 
which he has “transferred” to the so-called ‘isomorph ”’ are 
neither “generically” nor specifically “differentiated” from 
the species under consideration, that, histologically and im- 
ternally, the perforated and canaliferous specimens are iden- 
tical with those stated to be “imperforate” and without the 
septum. 
External Conformation. 
Few Palliobranchs have so singular an appearance as Spe- 
rifer cuspidatus. While its spiriferal valve deviates in no 
marked degree from ordinary species, being semielliptical and 
flatly convex, its opposite one is characterized by an erect 
elevated umbone and an enormously developed area, which 
give quite a pyramidal form to the shell. 
Instead of being incurved, as is usual, the umbone displays 
more tendency to the opposite character, or to become twisted, 
like that of Streptorhynchus. The area varies in outline be- 
tween an equilateral and an acute isosceles triangle, and, as 
in most Spirifers, it is both transversely and longitudinally 
marked with faint lines. The deltoid fissure is well exhibited; 
but whether it was closed in all its length with a deltidium, 
as is the case in the allied Sp. distans, Sowerby, or merely in 
its lower part, is a point which I am unable to determine. I 
have represented in Pl. IT. fig. 1 a specimen of Sp. cuspidatus 
presented to the Geological Museum of Queen’s College, 
Galway, by my very respected colleague, Dr. M‘Coy, Professor 
of Materia Medica, which shows, what is rarely exhibited, the 
deltoid fissure near its base covered with a number of arching 
lamella ; but nothing of the kind occurs higher up: so there 
is just as much reason for concluding that the upper part has 
been destroyed as that it never existed. If, as appears to be 
the case, the semicircular space below the arching lamelle has 
served as a foramen or opening for the pedicle, the cireum- 
stance would afford some ground in favour of the first con- 
clusion*, and consequently of the species being furnished with 
a deltidium like that of Sp. distanst. 
Both valves are marked with numerous fine ribs, which, 
however, occasionally become obsolete; and this is generally 
the case on the median folds. 
* T would suggest to American paleeontologists who have an opportu- 
nity of collecting casts of apparently this species, abundant in the Car- 
boniferous sandstone in the State of Ohio, to examine impressions of the 
area, when, no doubt, they will be able to determine whether the deltoid 
fissure is partially or completely closed. 
+ Several of Mr. Davidson’s figures represent specimens of this species 
with the deltoid fissure completely closed. (See Mon. Brit, Carb. Brach. 
pl. 8, and Geol. Mag. July 1867, pl. 14. figs. 7 & 9.) 
