44 



STUDIES IN BIOLOGY. 



EXPLANATION OF PLATES. 



p ad 



Posterior adductor. 



m n 3 



Third marginal nerve. 



a ad 



Anterior adductor, 



p n 



Pedal nerve. 



a rt 



Anterior retractor. 



b n 



Byssal nerve. 



p rt 



Posterior retractor. 



gn 



Gill nerve. 



m rt 



Middle retractor. 



t n 



Tentacular nerve. 



rft 



Retractor of the foot. 



d m n 



Dorsal marginal nerve. 



fl 



Foot. 



a ao 



Anterior aorta. 



olp 



Outer labial palp. 



p ao 



Posterior aorta. 



il p 



Inner labial palp. 



ap a 



Anterior pallial artery. 



j m ' 



Junction of mantle. 



pp a 



Posterior pallial artery. 



gd 



Genital duct. 



a m a 



Anterior marginal artery. 



ogd 



Organes godronnes. 



p m a 



Posterior marginal artery 



mes 



Mesosoma. 



ven 



Ventricle. 



bys 



Byssus. 



aur 



Auricle. 



man 



Mantle. 



a b 



Aortic bulb. 



stm 



Stomach. 



a v a 



Anterior ventral artery. 



pc 



Pyloric caecum. 



p v a 



Posterior ventral artery. 



int 



Intestine. 



g a 



Gastro-intestinal artery. 



re int 



Recurrent intestine. 



t a 



Tentacular artery. 



dir int 



Direct intestine. 



p a 



Pedal artery. 



red 



Rectum. 



tr a 



Transverse artery. 



gul 



Gullet. 



r a 



Recurrent artery. 



i( J 



Inner gill. 



Iv 



Longitudinal vein. 



og 



Outer gill. 



O V 



Oblique vein. 



eg 



Cerebral ganglion. 



h v 



Horizontal vein. 



vg 



Visceral ganglion. 



m s 



Marginal sinus. 



pg 



Pedal ganglion. 



a v 



Anatomosing vein. 



C V c 



Cerebro-visceral connective. 



asc v 



Ascending vein. 



c p c 



Cerebro-pedal connective. 



coul 



Couloir pericardique. 



m n 



Marginal nerve. 



per 



Pericardium. 



m 11 1 



First marginal nerve. 



i Ij 



Interlamellar junction. 



m n 2 



Second marginal nerve. 



*fj 



Interfllamentar junction. 





Plati 



: I. 





Fig. 



1. Diagrammatic section of M. lotus. 



2. Ventral view of M. latus. The mantle-lobes are separated, and the gills are cut off 



near their base. 



3. Ventral view of M. cdulis, as above. 



Plate II. 



4. Shell of M. latus, showing muscle-impressions. 



5. Shell of M. edulis, as above. 



6. Shell of M. latus, lateral view. 



7. Shell of M. latus, dorsal view. 



8. Sections through the dotted lines in Fig. 7. 



Plate III. 



9. Muscles of M. latus, lateral view. 



10. Muscles of M. latus, dorsal view. 



11. Muscles of M. edulis, lateral view. 



12. Alimentary canal of Dreissena, after Van Beneden. 



* 

 Plate IV. 



13. Alimentary canal of M. latus, dorsal view. 



14. Alimentary canal of M. latus, lateral view. 



14a. Underside of stomach of M. latus, showing cardiac csecurn. 



15. Alimentary canal of M. edulis, after Sabatier ; stm — utricular stomach of Sabatier, 



and p c — tubular stomach of Sabatier. 



16. Alimentary canal of M. edulis, after Sabatier. 



