298 H. Etheridge, jun. — On some new Carboniferous Conchifera. 



Locality. — Found by Mr. J. BeBnie in the shales of the Orchard 

 Cement Stone (Upper Limestone series), at William-wood, about 

 three miles south of Glasgow. 



2. — For an opportunity of noticing the following species of 

 Pteronites, McCoy, I am indebted to Mr. J. Young, of Glasgow, who 

 first called my attention to it. It approaches in many of its characters 

 P. persulcatus, McCoy, but is smaller and differs considerably in the 

 ribbing of the shell. I propose for it the specific name P. regularis. 

 In P. persulcatus the ribs are coarse, rugged, flexuous, irregular, 

 slightly interrupted ridges, larger and smaller. The ribs in the 

 new species show no alternation in size, are equal, sharp, regular, 

 and much finer and more numerous in proportion to the size of the 

 shell ; neither do they show any tendency to become rugged and 

 broken up, as in McCoy's species, but pass direct from one end of 

 the shell to the other. In P. persulcatus the ribs on the posterior 

 wing are larger, and separated by broader interspaces than those on 

 the body of the shell, but in our new form, P. regularis, there is no 

 apparent difference, all the ribs possessing the same flexuous even 

 aspect. Its characters are as follows : 



Pteronites regularis, sp. nov. — Shell transversely -trigonal, de- 

 pressed; anterior end small, pointed; posterior end thin, delicate, 

 apparently subtruncate ; hinge-line well defined, about equal to the 

 width of the shell; beaks sharp, nearly terminal, slightly prominent; 

 ventral margin without any visible sinus ; shell thin ; surface with 

 numerous regular, sharp, fiexuous, equal, persistent ribs, which pass 

 in a close unbroken manner from one side of the shell to the other. 



Localities. — Arden Quarry, near Thornliebank, Eenfrewshire ; 

 Linn Sj)out Quarry, Dairy, Ayrshire; at both localities in shale 

 under the Thornliebank and Arden Limestones (Upper Lime- 

 stone series) associated with Esther ia punctatella, Jones. 



3. — The generic affinities of the next species do not appear to be 

 as clear and decided as those above described, and the creation of 

 a new genus for its reception, on the strength of the only single 

 specimen with which I am acquainted, would be rather hazardous, 

 especially as some of the characters are not sufficiently well marked. I 

 have provisionally referred it to Schlotheim's Myacites. The absence 

 of an erect dorsal margin at once excludes it from Sanguinolites, 

 McCoy, and Edmondia, de Koninck. In neither of these shells is 

 the tapering of the posterior side so marked as in the present species ; 

 even in the presence of an erect dorsal margin it would not be 

 prudent to refer it to the latter genus without some indication of 

 the hinge mechanism. In form, the shell at present under con- 

 sideration approaches nearest to Myacites, possessing the exact out- 

 line of many Secondary species of that genus. The presence of 

 Myacites in palaeozoic rocks is a debated point, but as it is sanctioned 

 by Prof. Morris in his ' Catalogue,' it must be retained until a better 

 genus is proposed for the shells at present included in it. Prof. 

 King considered Myacites equivalent to his Allorisma (Perm. Foss., 

 p. 196), and proposed the substitution of the one term for the other, 

 the only reason assigned for this change being that the name Myacites 



