66 



Guide to the Invertehrata. 



GALLERY The outer edges of the mantle-folds are set with bristles ('' 



East Side These structures are shown in Diagrams 5 and 11. 



Wall-cases 

 lO&ll, 

 Table, 

 cases 



Fig. 99. — Camarophoria Schlotheimi, Buch, sp. Permian. Ventral side of 

 internal cast, showing the impressions of vessels in the mantle-fold. 



Muscles pass across the body of the animal from one shell-valve 

 to the other (Diagram 6) ; they serve to open and to close the 

 valves, and to move them sideways. The attachment of these 

 muscles to the shell forms scars, and in fossil Brachiopods these 

 scars are the only evidence we have as to the arrangement of the 



V D 



Fig 100. — Lingula anatina, Lamk. Recent seas. Interior of V, ventral or 

 peduncular valve, and D, dorsal or brachial valve, to show muscle-scars, 

 which are denoted thus : «. urabonal ; p.s. parietal ; tm. transmedian ; 

 e.-l. externo-lateral ; m.-l. medio -lateral ; c. central; a. -I. antero -lateral. 



muscles. It is therefore important to understand the meaning 

 of these scars; and to help the student, a very careful drawing 

 from life of the inner surface of a Lingula shell has been made 

 (Diagram 7 and Fig. 100), which may be compared with the adjacent 

 diagram showing the muscles. 



