1144 



THE ANATOMY OF SCAPHULA. 



Shell. — -Minute, elongated, thin, closed and deep posteriorly. 

 Anteiioi" margin slightly convex, and sloping backwards from 

 above and continiioiis with the ventral margin. Yentral margin 

 slightly convex in front, straight or very slightly convex behind 

 and somewhat sloping downwards. Posterior mai-gin convex and 

 sloping downwards and backwards. Ligamentous area small, 

 narrow, triangular in front of and broadly club-shaped behind 

 the umbones. Ligament lozenge-shaped and occupying the 

 anterior and a small area of the posterior portion of the 

 ligamentous area, and half the length of the entire ligamentous 

 area. Hinge teeth numerous. Central teeth obsolete. Four or 

 five lateral teeth, oblique in direction. Three posterior lateral 

 teeth elongated and very oblique. Surface with a thin, light- 

 brown epidermis. Diagonal ridge very prominent. Surface in 



Text-fio;ure 7. 



8 9 10 



Atiinial of S. minuta, sido view (left). 



front of the ridge convex, and with fine radiating and horizontal 

 lines intersecting one another. Surface behind the ridge concave, 

 and with four stout radiating ridges in addition to minute, closely 

 placed similar lines all intersected by vertical ones. Length 

 4-5 mm., height 2 mm., trans, diam. 2 mm. 



The present species diS"ers from the three other known species 

 of Scaphula, Benson in its minute size, in the slight tumidity of the 

 valves (the proportion of the vertical diameter to the transverse 

 diameter being 1:2), and in the compai-ative shortening of the 

 body in the antero-posterior diameter. 



The type-specimens are kept in the Indian Museum. 



Exjolanation of Text-figures 1-7. 



1. Anterior adductor muscle. 2. Posterior adductor muscle. 3. Posterior 

 retractor pedis muscle. 4. Free end of the rectum. 5. Stomach. 6. Outline of 

 the liver. 7. Labial palp. 8. Foot. 9. Visceral mass. 10. Byssus threads. 

 11. Ventral fissure of the foot. 12. Ventricle. 13. Auricle. 14. Rectum. 

 15. Ciliarj' discs. 16. Filament of inner demibranch. 



