MUSCULAR AND ALLIED SYSTEMS. 99 



C. 39. A vertical section through the umbo of a Scallop (Pecten 

 maximus), showing the position and direction of the ad- 

 ductor muscle. 0. C. 51 A. 



C. 40. A vertical section of the valves of an Oyster (Ostrea edulis), 

 showing the adductor muscle and the disposition of its 

 fibres at right angles to the shell. 0. C. 50. Ilunterian. 



C. 41. The lower flattened valve of an Oyster, showing by a 

 transverse section the extent and shape of the adductor 

 muscle. 0. C. 51. Ilunterian. 



C. 42. Right valve of Anomia ephippium, showing the muscular 

 system. Close in front of the single adductor of the valves 

 is a large posterior retractor pedis which runs transversely 

 across the body from the left valve to the byssal plug. A 

 small fan-shaped muscle runs forward from the anterior 

 edge of the byssal ping and is attached to the right valve 

 near the hinge. There is also a small anterior retractor 

 pedis on the left side. 



v. Ihering. Zeitschr. f. wiss. Zool., Bd. xxx. 1878, p. 13. 



C. 43. A Tectibranchiate mollusc from which part of the dorsal 

 integuments have been removed to show a sheet of inter- 

 lacing muscle-strands beneath. 0. C. 62 A. 



C. 44. The muscular parts of an Ormer (Haliotis tuberci data) , 

 showing a modification of the columellar muscle related to 

 the sucker-like character of the foot. The muscle has tho 

 form of a massive truncated cone attached by its apex to 

 the shell slightly to the right of the mid-line and spreading 

 out below to form the substance o the foot. A section 

 of the muscle has been cut to show its dense felted texture. 

 0. (J. 53 B. Presented by F. Hutchesson, Esq. 



C. 45. The muscular system of a Limpet (Patella vulgata), 

 showing a somewhat similar modification of the columellar 

 muscle. At its origin, the muscle has the form of a back- 

 wardly directed horseshoe, from which the muscle-fibres 

 pass directly into the foot converging towards the mid-line. 



H2 



