ANIMAL TO ITS SHELL IN SOME EOSSIL CEPHALOPODA. 103 



of each impression is situated on the edge of the impressed zone, so that about one- 

 third of the width of the impression is on the impressed zone, the other two-thirds 

 being on the inner area of the whorl. The two impressions are nearest together at about 

 half their length ; they are here 19 mm. apart, while the posterior extremities of their 

 inner boundaries are 32 mm. apart. The length of each impression (measured from the 

 anterior extremity of the inner branch of the lateral saddle) is about 50 mm. ; the 

 greatest width being 17 mm. No traces of the annulus have been observed in this 

 specimen. In the middle of the peripheral area, and extending a short distance into the 

 peripheral lobe, there is a broad, faint, longitudinal depression about 25 mm. long and 

 3'0 mm. wide, slightly wider anteriorly than posteriorly. Possibly this had something 

 to do ^^'ith the muscular attachment of the animal to its shell. On one side of this there 

 is a narrower, shorter, and less distinct longitudinal depression. 



AsPiDOCERAS, Zittel. 



Aspidoceras sp. — Among the si^ecimens which Dr. J. W. Gregory collected from 

 " below Chamgamwe, opposite Mombasa Island," East Africa, there is a fragment of an 

 Aspidoceras which displays the muscular impression ; it is merely the natural cast of the 

 posterior part of the body-chamber, and this is incomplete on one side (PI. 19. iigs. 6, 7). 

 The section of the base is obtusely cordate, and measures about 43 mm. in width and 

 34 mm. in height. The impression is seen on the inner area of the whorl as a faintly- 

 impressed line, which, ai'ising from the edge of the impressed zone (corresponding to the 

 suture of the shell) at a point about 15 mm. in advance of the base of the body-cliamber, 

 passes outward, describing a curve slightly convex forward, and when at a distance of 

 9'5 mm. from the edge of the impressed zone jiasses backward nearly parallel to this 

 edge for a distance of at least 10 mm. It then seems to divide into several very 

 faint grooves which are continued backward nearly to the base of the body-chamber. 

 No indications of the annulus can be seen. Unfortunately the cast is very imperfect 

 on the opposite side. 



C O S M C E R A T I D .E, Zittel. 



Parkinsonia, Bayle. 



Parkmsonia Parkinsoni, J. Sowerby, sp. — The muscular impressions are well shown in a 

 Avell-preserved example of this species in the British Museum Collection (No. 9) from the 

 Inferior Oolite of Bayeux (Calvados), Prance. PuUy two-thirds of the outer whorl are 

 occupied by the body-chamber ; the test having been removed from the greater part of 

 this chamber, the internal cast is well displayed. The dimensions of the specimens 

 are : — diameter of shell 213-5 mm. ; width of umbilicus 58 mm. ; height of outer whorl 

 49 mm. ; greatest thickness of ditto o2'5 mm. The body-chamber appears to be fairly 

 complete ; its length measured along the median line of the periphery is 287 mm. ; 

 and the dimensions of its base are : — height 31'5 ram., greatest thickness (which 

 is at about one-third of the height of the whorl from the inner edge) 22-5 mm. 

 The muscular impression on each side can be seen. At the suture of tlie shell the 



SECOXD SERIES. — ZOOLOGY, VOL. VII. 15 



