Prof. W. King on Spirifer cuspidatus. 17 
In the first stage in the process of rubbing down the umbone, 
the section (Pl. IIT. fig. 17), at the depth of one-eighth of an 
inch, displayed the dental plates (a) and the septum (4); the 
latter was nearly on a line with the area. In the second (fig. 18), 
at the depth of a quarter of an inch, the septum was more clearly 
distinguished as an independent structure; and its centre showed 
a trace of the canal (c). In the third (fig. 19), half an inch in 
depth, the septum was placed much further in, and the canal, 
now more obvious, was situated in the centre of its back. In 
the fourth (fig. 20), five-eighths of an inch, the canal, hitherto 
filled with a shelly deposit, was well displayed, and exhibited 
evidences of a foreign-mineral infilling. In the fifth (fig. 21), 
three-quarters of an inch, the septum was somewhat reduced 
in thickness, but the canal was larger and well filled with 
adventitious matter. In the sixth (fig. 22) seven-eighths of 
an inch, the septum had disappeared ; the canal, however, was 
still present. In the seventh (fig. 23), one inch, the tube was 
getting faint; still the dental plates were seen crossing the 
entire width of the umbonal cavity. In the eighth and final 
stage, one inch and an eighth, both the canal and the central 
portion of the dental plates were gone. 
It is thus evident that the septum and canal were an early 
development—that the latter became gradually filled up with 
a shelly substance in its oldest part, but remained open for 
about three-eighths of an inch at its distal extremity—that the 
canal projected beyond the free margin of the septum for about 
a quarter of an inch, and terminated on a level with the centre 
of the free margin of the dental plates. 
These points are exactly in accordance with the appearances 
presented by a beautiful fossil cast, from the State of Ohio, for 
the loan of which I feel much indebted to Mr. Davidson : in- 
deed the resemblance is such as to strongly impress me with 
the idea that the cast belongs to a shell specifically identical 
with Martin’s Spirifer cuspidatus. 
The canal of Spirifer distans, according to Davidson’s figure, 
also remains open at its extremity ; and such is the case in the 
Galway specimen of this species (fig. 10) ; it appears, however, 
to be more incomplete, and to rise more from the back of the 
septum, than the one belonging to Spirifer cuspidatus. 
Some additional investigations which I have recently made 
among a number of other Spirifers may now be brought under 
notice. As Spirifer striatus is the type of the genus*, I am 
induced to give some details of its corresponding apophysis. 
* This has been shown to be the case by Mr. Davidson, in the Intro- 
duction to his ‘ British Fossil Brachiopoda,’ p. 81. 3 
Ann. & Mag. N. Hist. Ser.4. Vol. in. 2 
