ANIMAL TO ITS SHELL IN SOME FOSSIL CEPHALOPODA. 83 



area, passing into a shallow groove on tlie concave portion of the body-chamber, but the 

 part of the latter between the groove and the anterior ini]n"essed line produced by the 

 ornaments of the septate part of the shell is covered with a thin, yellowish, powdery 

 layer, quite unlike the rest of the concave portion of the body-cbamber. This in all 

 probability indicated tlie place of attachment of the shell-muscles. 



I bave not observed tlie remains of tbe annulus iji any example of this species that 

 has come under my notice. 



TuKKiLiTES, Lamarck. 



Tm'7'ilites tuberculatus, Bosc. — An example of this species in tbe Museum of Practical 

 Geology (No. 6372) from the Lower Chalk of Cliffe Anstey, Wilts, displays tbe anterior 

 border of the muscular scars exceedingly Avell (PI. 18. ligs. 1, 2). Tbe specimen is a 

 natural internal cast of about live Avliorls, the smallest of whicb is somewhat imperfect, 

 and the rest fairly well preserved. Two of the upper wliorls show that the sipbuucle [si) 

 is situated at about one-sixth of tbe height of the whorl below the suture of the shell. 

 Unfortunately the suture-line is not well shown, so that it is not possible to say exactly 

 where the body-chc^mber commences. Tbe aperture is fairly well preserved. The height 

 of the last whorl (from the lowest of the three rows of small tubercles to tbe suture of 

 tbe shell) is about 52 mm. ; the Avidth of the whorl (/. e. the distance across the specimen) 

 being 1085 mm. Tbe anterior border of the muscubu- attachment is well shown on the 

 last whorl as a well-marked narrow groove. VicAving the specimen with the aperture away 

 from you and directed downward, tbe course of this groove may be thus described : — 

 Commencing somewhat below the centre of the whorl it passes for a very short distance 

 (about 2 mm.) downward and to the right ; then, turning still more to the right, it passes 

 for a distance of about 13 mm. with a bold convex curve to within 12-5 mm. of the 

 lowest row of smaller tubercles ; then turning again still more to the right it glasses 

 under the uppermost row of small tubercles. Just beneath the tubercle to the left of 

 the one under which this groove passes there are indications of a septal suture ; this is 

 believed to be the last septum, and therefore to indicate the commencement of the body- 

 chamber. Passing still to tbe light and down\Aard in a broad feebly-convex curve, and 

 at the same time becoming deeper, the groove crosses the two lower rows of small 

 tubercles at about 30 mm. from the last-mentioned bend ; it is continued on to the 

 surface below the tubercles until at about 10 mm. below the lowest row it curves round 

 in a broad curve and passes to the left for a short distance; then at about 21 mm. below 

 the lowest row of tubercles it makes an angular bend, passes downward and to the left 

 for a distance of 11 mm., when it curves upward and passes into the umbilicus ; this 

 upward portion can be traced for about 2'1< mm., when it is obscured by matrix. With 

 the exception of the 15 mm. first described, probably the whole of this incised line 

 represents the anterior boundary of the two muscular scars. 



Turi'ilites Mantelli, Sharpe. — An imperfect example of this species in the Museum of 

 Practical Geology (No. 0373), from the Lower Chalk of the Isle of Wight, also shows a 

 portion of the anterior border of one of the muscular scars (PI. 18. fig. 3), The specimen 



