112 MR. G. C. CRICK ON THE MUSCULAR ATTACHMENT OF THE 



Perisphinctes Achilles, d'Orbigny, sp. (p. 102). 



Fig. 5. Left lateral aspect. The boundary of the muscular scar is seen on the inner portion of the 

 outer whorl opposite the small arrow. 



Aspidoceras .«/*. (p. 103). 



Fig. 6. Dorsal aspect of a fragment of the body-chamber. 

 7. Right lateral aspect of the same. 



Arietites obtusus, J. Sowerby, sp. (p. 93). 

 Fig. 8. Left lateral aspect of a portion of a specimen, showing the muscular scar on the inner portion 

 of the outer whorl opposite the arrow. 

 9. Right lateral aspect of the same. 

 10. Ventral aspect of the same, showing the liuguiform impression on the central portion, and 

 anterior to it an /-shaped incised line in the depression on each side of the keel. 



Lytoceras fimbriatum, J. Sowerby, sp. (p. 91). 



Fig. 11. Dorsal aspect of the posterior portion of the body-chamber, exhibiting the left and a portion 

 of the right muscular scar. 

 12. Left lateral aspect of the same. 



Lytoceras cornucopite, Young & Bird, sp. (p. 91). 



Fig. 13. Dorsal aspect of the posterior portion of the body-chamber. 



14. Right lateral aspect of the same. 



15. Right lateral aspect of another specimen, showing the small oval scar on the inner part of the 



outer whorl opposite the aiTOw. 



16. Portion of same enlarged, showing muscular scar. X f . 



17. Ventral aspect of portion of same enlarged, exhibiting the linguiform impression, x "f . 



Plate 20. 



Peltoceras sp. (p. 102). 

 Fig. 1. Dorsal aspect of fragment, showing the two elongated muscular scars. X ^. 



^goceras capricorimm, Schloth., sp. (p. 95). 



Fig. 2. Right lateral aspect. The muscular scar is the small white patch on the inner portion of the 

 outer whorl opposite the arrow. 



j^goceras laqueolum, Schloenbach, sp. (p. 96). 



Fig. 3. Dorsal aspect of fragment of body-chamber, showing the left muscular scar and part of the 

 right. 



4. Left lateral aspect of the same. 



