22 
PALAEONTOLOGY OF NEW YORK. 
however, there is a distinct development of the septum in this anterior portion 
of the shell,'such as is also to be found in both valves of some Trimerellas. 
The posterior outline of the muscular region in the pedicle-valve is very 
striking. It consists of a central lobe or scallop, at each side of which is a 
somewhat broader lobe, continuous with the faintly defined lateral muscular 
scar. It seems evident that this lobed impression, which has been aptly 
compared, by Davidson and King, to a Moorish arch, is of muscular origin 
and made by separate muscular bands. This appears from the fact that we 
shall have to consider the crescent as the base of attachment of the parietal 
walls. There is nothing, however, in Lingula or in the Trimerellids from 
which an homology can here be satisfactorily elicited. While we should be in¬ 
clined to regard the impression as entirely a muscular scar, we may quote the 
remarks of the authors above referred to: 
“ The middle sinus, we have little doubt, has been produced by the umbonal 
muscle pressing against the post-parietal or posterior wall of the splanchnocoele. 
It may be suggested that the lateral sinuses have been formed in the same way 
by other muscles, but as Lingula is not characterized by any similarly situated 
(at least in the brachial valve # ), we prefer the idea that they represent certain 
viscera; and they may be recesses produced by the pressure of the ovarian 
lobes against the inner side of the post-lateral walls of the splanchnocoele ” 
(pp. 166, 167). 
The validity of this speculation apparently rests, to a great degree, upon the 
conception of the authors, that the valve under consideration is not the pedicle- 
in the middle, due, we believe, as in Lingula, to this portion having been forced out by the pedicle; while 
the crescent in the brachial valve has a pointed crown directed backward; now it is this peculiarity that 
plainly presents itself in Lingulops.” Again: “ In the Trimerellids, as in Lingula, the pedicle-valve has 
a short, rudimentary median plate,whereas in their brachial valves this part is well developed and elongated, 
as it evidently is in Lingulops.” Considerable importance is given by the authors to the discussion of the 
character and function of what they have termed the “semicircular zone,” which we regard as the broad 
inner moiety of the cardinal area, more extremely developed in Monomerella and Rhinobolus. The sugges¬ 
tion is made that it is homologous with that area in the brachial valve of Lingula occupied by the setal band. 
We have preferred to consider the original valve as the ventral or pedicle-valve, partly on account of the 
pedicle-groove, which is certainly better defined than it appeared to Messrs. Davidson and King, as well as 
from incontrovertible evidence derived from the opposite valve, which at that time was unknown. 
* “ In the pedicle-valve of Lingula anatina the transmedian muscles have their attachment similarly 
situated. Were the fossil the same valve, we should have had little hesitation in referring the lateral sinuses to 
these muscles, notwithstanding their being single on one side and double on the othei' in Lingula." 
