G. C. Crick — On Cyrtocerasfrom Derhyshir'e. 65 



preserved ; this appears to have been simple and nearly parallel 

 to the base of the body-chamber. The septa are oblique, tilted 

 up on the dorsal side; the chambers are shallow, the sutures being 

 about 5 mm. apart at the middle of the ventral aspect, or outer 

 curvature of the shell. There is no thread-like line or keel in the 

 centre of the ventral aspect. The siphuncle is not clearly shown ; 

 it seems to have been inflated between the septa and to have been 

 exogastric, i.e., situated near the ventral surface of the shell. The 

 test is not preserved. 



The characters of the specimen agree so closely with Foord's 

 Cyrtoceras (MeJoceras) aptcale that I think it may be correctly 

 referred to that species. Hitherto the species has been recorded 

 only from the Carboniferous Limestone of St. Doulagh's, co. Dublin.^ 

 Dr. Hind's fossil is interesting, therefore, as showing the occurrence 

 of the species in this country also. It possesses additional 

 interest from the fact that it partially exhibits the form of the 

 muscular attachment of the animal to its shell. In the middle of 

 the less convex (or dorsal) surface of the body-chamber there are 

 portions of two elliptical longitudinally-elongated areas,' each about 

 18 mm. wide ; they touch each other in the median line of the 

 ventral surface at a point 33 mm. below the edge of the aperture, 

 part of which is also well shown in this fossil. Their anterior 

 borders are 23 mm. from the edge of the aperture ; both areas are 

 imperfect posteriorly owing to the imperfection of the specimen, and 

 for the same reason their exact position with reference to the last 

 septum is not indicated, but it is estimated that the point at which 

 these two elliptical areas meet was about 23 mm. in advance of the 

 last septum, their anterior borders being about 10 mm. nearer the 

 margin of the aperture. These elliptical areas are evidently the 

 impressions (on the natural internal cast) of the muscle-scars that 

 existed on the internal surface of the dorsal portion of the shell. 

 The condition of the surface of the specimen prevents us from 

 recognising any indication whatever of the band connecting these 

 two areas across the ventral surface. They are exactly comparable 

 with the muscle-scars previously described in the genus Amphoreopsis.^ 

 EXPLANATION OF PLATE III. 

 Cyrtoceras {Meloceras) apicale, A. H. Foord. 

 Fig. 1. — Dorsal aspect, exhibiting portion of peristome or margin of aperture [a), 

 and part of the boundaries of the two muscle-scars [sm), Is being (in all the 

 figures) the last septum or base of the body-chamber. 



,, 2. — Right lateral aspect, showing part of the peristome {a) and a small portion 

 of the boundary of the right muscle -scar {sm). 



,, 3. — Ventral aspect, showing a portion of the margin of the aperture («). 



,, 4. — Left lateral aspect, displajdng part of the margin of the aperture (a) and 

 the boundary of the left muscle-scar {sm). 



Carboniferous Limestone : Kniveton, Derbyshire. 



In the collection of Dr. Wheelton Hind, F.G.S. All the figures are di-awn of about 



three-fifths the natiu-al size. 



1 A. H. Foord: Mon. Garb. Ceph. Ireland (Pal. Soc), pt. ii, 1898, p. 36. 



2 A portion of the boundary of each area is indicated by a very obscure feebly - 

 impressed Kne. 



3 G. C. Crick: Proc. Malac. Soc, vol. vi, pt. 3, Sept. 1904, pp. 134-7, pi. viii. 



DBCADE V. — VOL. II. — NO. II. 5 



