so ME. G. C. CEICK ON THE MUSCULAE ATTACHMENT OF THE 



only fragments of the test adliering to it. At the base of the body-chamber the whorl 

 is subquadratein section, its height being 35 mm., and its greatest width 31 mm. (PI. 17. 

 figs. 12, 13). The imi:)ressions are not so complete as in the example just described. The 

 anterior margin of each is indicated by a sharply-incised line ; both lines almost meet each 

 other in the median line of the inner (dorsal) area at about 10 mm. anterior to the summit 

 of the innermost portion of the saddle on either side of the antisiphonal lobe. Dis- 

 appearing posteriorly, each passes forward and outward for a length of about 10 mm., when 

 each is about 5 mm. in advance of its origin ; then, turning abruptly backward, each 

 gradually disappears at a distance of about 9 mm. from its point of origin and about 

 14 mm. from the median line. The posterior extremity of each has a tendency to turn 

 outward, and at a short distance from the extremity the line gives off a very faint branch 

 wdiich turns inward, but can be traced only for a short distance. Without doubt the 

 faint line turning inward represents the boundary of the impression of the shell-muscle, 

 and that continuing in an outward direction indicates the position of the anterior border 

 of the adjacent portion of the annulus. 



Ancyloceeas, d'Orbigny. 



Ancyloceras Matheronimmm, d'Orbigny. — In the genus Aucyloccras what is be- 

 lieved to be the impression of the mviscular attachment of the animal has been best 

 seen in an example of Ancyloceras Matlieronimmm in the British Museum Collection 

 (No. 0. 5322). It is a natural internal cast from the Neocomian of Cassis (Bouches-du- 

 Pi,h6ne), France (PL 17. figs. 14, 15, 16). The coiled part of the septate portion is wanting, 

 but the rest is fairly well preserved, although much waterworn. The body-chamber, 

 measured along the centre of the periphery, is 380 mm. long ; the cross section of its base 

 is oval, the dorsal (or inner) portion being somewhat wider than the ventral (or outer) ; 

 the veutro-dorsal diameter (or height) of the base is 75 mm., the transverse diameter 

 {i. e. the thickness) 54 mm. (excluding the tubercles). What I regard as the impressions of 

 the boundaries of the two muscular scars are seen on the inner or dorsal area. The two 

 scars are not quite symmetrical, that on the right side extending about 15 mm. further 

 forwards than that on the left. These boundary-lines are incised, but they are much 

 coarser than usual. This, however, is probably due to the -waterworn condition of the 

 specimen, for the septal sutures, instead of being iinely -incised lines as usual, are fairly 

 deep and wide, and indeed have quite the appearance of having been considerably water- 

 worn ; and this condition of the septal sutures suppoi'ts the opinion that the lines about to 

 be described are really the impressions of the boundaries of the muscular scars. That on 

 the right commences at about 3 mm. to the right of the median line and about 20 mm. 

 in front of the large saddle adjoining the antisiphonal lobe ; passing forward for about 

 35 mm. and approaching nearer the median line, it then turns outward, but still 

 continues forward until at about 50 mm. from the last septum, when it turns still more 

 outward and then disappears. That on the left appears to arise about 43 mm. in front 

 of the miost anterior portion of the saddle adjoining the antisiphonal lobe, and about 

 6 mm. from the boundary on the right side ; passing forward and outward for nearly 



