88 MR. G. C. CEICK ON THE MUSCULAR ATTACHMENT OF THE 



Cardiocerm Sidherlandice, J. cle C. Sowerby, sp. — The position of the anterior 

 boundary of the sbell-muscle is exceedingly well shown in a large example of this 

 species from the Oxfordian of Scarborough, Yorkshire. It forms part of the British 

 Museum Collection (No. 82369). It is a large internal natural cast, about 370 mm. (or 

 nearly 14f inches) in diameter, the umbilicus being 85 mm. in diameter, and having 

 almost perpendicular walls. Nearly one-half of the outer whorl is occupied by the body- 

 chamber, the base of wbich is obtusely cordate in section, 132 mm. (or nearly 5| inches) 

 high and 210 mm. (or rather more than 8J inches) wide, the inner area being 45 mm. 

 wide and nearly perpendicular to the plane of symmetry of the shell. The anterior 

 boundary of the muscular impression, represented by a well-marked groove, crosses the 

 umbiUcal margin 60 mm. (or about 2| inches) in front of the last septum, and passing 

 outward and backward becomes much less distinct at about 52 mm. from the last 

 septum, and at about the same distance from the umbilical margin. It appears, 

 however, to be continued across the whorl by a faint, somewhat irregular groove, which, 

 originating some 6 mm. posterior to the groove just described, crosses the whorl in a 

 flat forwardly-concave curve which is only 15 mm. from the anterior portion of the 

 lateral saddle, and nearly touches the anterior part of the external saddle ; this we 

 regard as the anterior boundary of the annulus. Passing inward from the umbilical 

 margin, the boundary of the shell-muscle is indicated by a distinct groove which 

 curves somewhat backward, but can be traced onlj'^ about halfway across the inner 

 area of the whorl. 



Cardioceras funifermn, J. Phillips, sp. — A similar boundary of the shell-muscle has 

 been observed in several examples of this species which are contained in the British. 

 Museum Collection. It is well shown in an example (No. 50447) from the Oxford Clay" 

 of Trowbridge, Wiltshire. This is 167 mm. in diameter and 68 mm. thick, the umbilicus 

 being almost closed and its margin rounded. About one-half of the outer whorl is 

 occupied by the body-chamber, the base of w^hich is acutely cordate in section, 64 mm. 

 wide and 72 mm. high. On the left side of the specimen the anterior border of the 

 shell-muscle is indicated by a groove which crosses the umbilical margin at 9 mm. 

 anterior to the last septum ; passing backward and outward as a fairly wide groove for 

 about 10 mm., it then becomes shallower and wider. The posterior boundary of the 

 muscular scar is represented by a slightly raised ridge, which, passing from the umbilical 

 margin just above the last septum outward and forward, meets the lower boundary of 

 the anterior groove at a point 12 mm. from the umbilical margin. The anterior groove 

 appears to be continued across the whorl {i. e. to within 5 mm. of tiie periphery) as 

 an exceedingly faint groove, which indicates the position of tlie anterior border of the 

 annulus ; this is 8 mm. anterior to the lateral saddle, 10 mm. anterior to the external 

 saddle, and is depressed at each lobe. On the outer haK of the lateral area of the whorl 

 this boundary is partly indicated by remains of the test. 



On the right side of the specimen there are similar indications of the anterior boundary 

 of the muscular scar, but uo traces of the annulus. 



