ANIMAL TO ITS SHELL IN SOME FOSSIL CEPHALOPODA. 79 



on the internal cast) meet nearly in the middle line in an obtuse backwardly-directed point 

 whicli is 3*25 mm. in advance of the saddle on either side of the antisiplional lobe, these 

 two saddles occupying a large portion of the autisiphonal area. From this point each 

 Ijoundary passes forward and outward for a short distance, then turns backward and 

 sweeps over on to the lateral area in a broad anterioi'ly-convex curve whicli gradually 

 disajipears before reaching the last septum ; if continued to the septum it would meet 

 the large lateral lobe on its antisiphonal side. It would seem tlierefore that, just as in 

 the Baculites already described, the muscular scar on either side occupied the space 

 between the central line of tiie autisiphonal area and the antisiphonal side of the large 

 lateral saddle. There is no trace of the annulus in this example. 



Hamites, Parkinson. 



Samites viaximus, J. Sowerby *. — In the British Museum Collection (No. C. 6S02) there 

 is an example of this species, from the Gault of Folkestone, which displays the form of the 

 muscular scars exceedingly well (PI. 17. figs. 0, 7). It is only a fragment, /. e. one portion 

 (the larger) of the terminal hook, and consists of the internal cast of the last loculus and 

 of a portion of the body-chamber ; its length, measured on the pcrij)hery, is about 55 mm. 

 The whorl is subcircular in section, only slightly compressed, its ventro-dorsal diameter 

 (excluding the ribs) at the base of the body-chamber being 16 mm., and its transverse 

 diameter (also excluding tlie riljs) 15 5 mm. Tlie impressions of the muscular scars are 

 seen on the inner (dorsal) surface of the cast of the base of the body-chamber, one on 

 either side of the median line and disposed souieAvhat oldiquely, just as in the exara2:>le 

 of Crioceras quadraium already described in this paper {ante, p. 74). Each scar is 

 elliptical in outline, and enclosed by a very faintly-incised line ; its longer axis is inclined 

 to the median line of the dorsal surface of the body-chamber at an angle of about 45°; 

 its posterior boundary is only about 1"5 mm. anterior to the antisiphonal saddle of the 

 last septum. Anteriorly the impressions are 1 mm. apart. The longitudinal and trans- 

 verse diameters of each scar are 12 and 10 mm. respectively. At about the middle of 

 the outer portion of the boundary there is a slight angularity, which doubtless indicates 

 the position of the commencement of tlie anterior border of the annulus, but no other 

 traces of the annulus have been observed. In another example which is figured (PI. 17. 

 tigs. 8, 9) each muscular scar bears a small roughened patch, and there are indications of 

 a narrow band connecting the scars. 



Crioceiias, Leveille. 



Crioceras quadratumf, n. sp. — The muscular impressions in this genus have been 

 best observed in two examples of Crioceras quadratam from the Speeton Clay, Yorkshire. 

 One of these has already been described (see p. 74). The other forms part of the British 

 Museum Collection (No. 89102). It consists of the natural cast of the body-chamber with 



* J. Sowerby, Min. Con. vol. i. p. 138, pi. lxii.(1814). 

 t See footnote, ante, p. 74. 

 SECOND SERIES. — ZOOLOGY, VOL. VII. 12 



