CARBONIFEROUS FOSSILS OF IRELAND. 43 



by Humphreys under the above generic title, and distinguished from the true Monodontce, principally by their 

 more elongate form, brilliant colouring, and the want of an umbilicus. The surface is perfectly smooth. Length 

 about six lines; length of mouth two lines; diameter of last whorl two and a half lines. 



SCUTIBR.\NCHIA AXD CYCLOBRANCHIA. 



Those are remarkably well defined, not only from a consideration of their anatomy, but also in their tes- 

 taceous covering; their shells are all simply cup-shaped, never spiral, or very slightly so in a few aber- 

 rant forms, in which they differ from the Pcctinihranchiate Gasteropuda, or ordinary spiral univalves. The 

 genera Acroculia and Patella, are found in the carboniferous limestone ; the first is scarcely distinguishable from 

 the recent Capulus, or the Tertiary genus Brocchia, while the latter is a well-known recent genus ; although, I 

 must confess, that it appears to me that the shells we now call Patella in those rocks, do not really belong to the 

 present tribe, but are more nearly related to Umbrella of Lamarck ; it would require, however, more perfect 

 specimens than I have seen to settle the question, meanwhile I cannot do better than leave them in their pre- 

 sent position. 



Teochella. Sw. 



Infundibulum. Mont. 

 Gen. Ch. — Conical, patelliform; apex central; spire internal, of two or three whorls; umbilicus very 

 small, or none. 



Trochella prisca. M'Cof/. (PL VIL fig. I). 



Sp. Ch. — Conical, smooth ; height rather greater than half the diameter ; spire of four- flat whorls ; sutures 

 only indicated, on the outside, by an obscure depression ; apex mammillary ; mouth transversely elliptical ; um- 

 bihcus smooth, roundish ; circumference acute. 



This fossil, although rather common, appears to have passed hitherto unnoticed, or, as I have frequently 

 known it, mistaken for a cast of the umbilicus oi a. Nautilus biaiif/ulattis, or some such shell. The discovery 

 of several fine specimens, shewing the under side, with the mouth and umbihcus, first enabled me to point out 

 its true nature, and to characterize it as a distinct species. When the outer shell is removed, the internal spire 

 can be distinctly seen ; but when perfect, it is only indicated by the very slight convexity of the whorls, the 

 suture being completely covered by the external shell. Diameter one incli seven lines, height of spire eleven 

 lines. 



FiSSURELLA. Brug. 

 Gen. Ch. — Patelliform, apex perforated. 



FlSSURELLA ELONGATA. MCoy. (PL V. fig. 27)- 



Sp. Ch. — Length about twice the width, conical; sides parallel; extremities rounded; apex one-fourth 

 the length of the shell, from the anterior end ; surface decussated by equal, radiating, and concentric ridges. 



Although the perforation in the apex of this remarkable fossil is obscured by a ^breaking of the shell, 

 I have no hesitation in placing it in the present genus. It is very much elongated and compressed ; the extremi- 

 ties are rounded, the anterior being shghtly the broadest ; the anterior end is only one-fouith the length of the 

 shell, very convex ; the posterior end is slightly depressed, the sides rather concave ; the surface is marked with 

 regular, rounded, radiating ribs, which are decussated by concentric sulci, placed at equal distances with the 

 radiating ones, so as to give a regularly chequered appearance to the surface. Length nine lines, width four 

 lines. 



