86 Messrs. Hancock and Embleton on the Anatomy of Eolis. 



EXPLANATION OF THE PLATES. 



Plate I. 

 All the anatomical figures in this plate are from E. papillosa. 

 Fig. 1. Eolis papillosa, Johnst., a little above natural size. 

 Fig. 2. E. coronata, Forbes, nearly double natural size. 

 Fig. 3. E. olivacea, Alder and Hancock, four times natural size. 

 Fiq. 4. Section of the lips with buccal mass attached : a, outer lip ; t, inner 

 lip ; c, oesophagus ; d, corneous plates of buccal mass ; e, channel 

 of mouth ; /, circular belt of muscle at the attachment of outer lip ; 

 g g, muscles passing from the circular belt to foot and skin of head ; 

 h, muscular bands passing from circular belt to posterior margin 

 of horny plates ; i, foot. 

 Fig. 5. Vertical section of buccal mass, showing the muscles of the tongue, 

 the external layer being removed : a, muscle which assists in ro- 

 tating tongue forwards, arising from upper margin of horny plate, 

 and passing downwards to inferior surface of 6, muscle which ro- 

 tates the tongue backwards, being inserted by its ends into the 

 posterior end of tongue and into the inferior extremity of cutting 

 blades e ; c, muscle attached to both ends of tongue, which it will 

 approximate ; it will also assist a in rotating the tongue forwards ; 

 d, strong layer of short transverse muscles which bind together the 

 external layers of muscle, and form a fulcrum for the semicircular 

 rotators ; /, oesophagus ; g, corneous plates ; h, ridge of the tongue ; 

 i, cutting-jaws ; k, the hinge or fulcrum of horny plates; I, anterior 

 extremity of muscular cheek-mass. 

 Fig. 6. Nearly vertical section of buccal mass : a, horny plate ; a', cutting- 

 edge ; b, inner lip ; c, hinge or fulcrum ; c', transverse muscles that 

 close the jaws; (/, transverse muscles that open the jaws; e, inferior 

 transverse muscles that assist in closing the jaws ; /, wedge-shaped 

 mass of tongue, supporting spiny ridge and showing the two ex- 

 ternal layers of muscles ; g, muscular cheek-mass ; h, fold of lining 

 membrane of mouth; ii, outer lip; k k, circular muscular belt at 

 base of outer lip ; /, oesophagus. 

 Fig. 7. Upper aspect of buccal mass : a a, corneous plates ; h, muscular bands 

 on the external surface ; c, oesophagus ; d, transverse muscles be- 

 fore fulcrum ; e, transverse muscles behind fulcrum ; the dark line 

 between the two sets of muscles indicates fulcrum ; //, muscles 

 arising from upper part of horny plates, and passing down behind 

 mass of tongue marked a in fig. 5. 

 Fig. 8. View of cavity of buccal mass from above, the fulcrum being divided, 

 and the horny plates a a drawn apart ; a' a', cutting-edges of jaws ; 

 b, inner lip; c, spiny ridge of tongue ; d, wedge-shaped muscular 

 mass of ditto ; e, muscular cheek-mass ; /, flat upper border of 

 ditto ; g, anterior attachment of ditto to cutting-jaws ; h, folds of 

 lining membrane of mouth ; i, fulcrum of horny plates ; k, ante- 

 rior and posterior transverse muscles ; /, oesophagus. 

 Fig. 9. Upper aspect of buccal mass with superficial muscles removed : 

 a a, corneous plates ; b, triangular process forming fulcrum ; c, cut- 

 ting-edges of horny plates ; d, ridge dividing sm-face of fulcrum 

 into anterior and posterior parts ; e, muscle of left side which 

 passes down to be attached below to tongue-mass, fig. T ff]f, thin 

 layer of muscular fibres which pass from edge of horny plate, con- 

 verging to form longitudinal fibres for oesophagus, g. 

 Fig. 10. Lateral aspect of buccal mass obliquely viewed, with part of the 

 muscles removed : a, exposed surface of corneous plates ; b, poste- 



