176 PROCEEDINGS OF THE GEOLOGICAL society. ([Dee. 1, 
producing either three or five plaits on the elevation ; but notwith- 
standing this irregularity, the division of the mesial fold mto two 
equal or nearly equal parts by a sharp deep sinus is never lost, and 
the additional plait remains smailer than its fellows. 
M. de Verneuil has united to the S. diforatus a species which 
appears to differ from it essentially in the points just described; the 
S. dentatus* has three equal plaits on the mesial fold and two equal 
plaits in the sinus: it thus wants the most important and constant 
character of the American species, the division of the mesial lobe 
into two equal parts by a deep sinus, and it must in consequence be 
regarded as a distinct species; in fact M. de Verneuil himself seems 
to have some doubts of the propriety of unitmg themt. 
The shell given by Mr. M‘Coy for Spzrifer lynzxt is figured with 
three equal plaits on the mesial fold, and must therefore be considered 
as the S. dentatus. 
The 8S. terebratuliformis of M‘Coy§, which has been given in 
Professor Sedgwick’s lists of Coniston and Welsh species under the 
manuscript name of S. crucialis without description, is closely allied 
to the S. biforatus, but is easily distmguished ; it has an elevated 
. plait along the middle of the mesial fold, forming a striking contrast 
to the deep sinus which occurs in the same situation in the S. bzfora- 
tus: this plait is accompanied in S. terebratuliformis by a pair of 
lateral plaits which usually bifurcate while the central one remains 
simple, so that the mesial fold has either three or five plaits. Besides 
this difference, the S. terebratuliformis has its plaits on the wings 
bifurcated. 
I have not been able to find any sufficient evidence of S. b:foratus 
having been found in this country. Professor Sedgwick quotes it 
from Pwllheli in Carnarvonshire||, but I have learnt that the shell 
there referred to is the S. terebratuliformis. Mr. M‘Coy states 
that the S. lynx is common in the county of Kildare, but his figure 
as above explained appears to represent the S. dentatus: the latter 
species has also been found in the Wenlock limestone of Dudley, 
&c., where it has been called S. lynz. 
(11) SprrirER MAcRoNotus, Hall sp.—Mr. James Hall has 
published a species of Spirifer under this specific name, which ‘is 
readily distinguished by the broad area, the narrow aperture, and the 
numerous small plain ribs and strong concentric lamine of growth J.” 
We have the same species in Europe, but have confounded it with the 
S. cuspidatus, from which it is easily distinguished by a greater 
number of ribs and a less elevated hinge-area terminating in a more 
obtuse angle ; moreover it never reaches the size of S. cuspidatus. 
In old and well-preserved specimens of S. macronotus about thirty 
ribs may be counted on each side of the mesial line, but in younger. 
specimens from fifteen to twenty only can be distinguished (while the | 
oldest specimens of S. euspidatus have only about sixteen ribs on 
* Russie, 1. a: fo: tT Russie, vol. ii. p. 138. 
< .Wil.. Foss: t.-3. 2 23: § Sil. Foss. t. 3. f. 26. 
|| Journ. Geol. Soc. vol. iii. p. 149. {| Hall, Report, pp. 206, 207, f. 3. 
