ON THE ANATOMY OF ENSIS (SOLEN) 

 MAGNUS, SCHUMACHER. 



By li. H. BLOOMER. 



By the kindness of Dr. Jensen of the Copenhagen Museum I have 

 been enabled to examine a specimen of J^J. maijnux. 



EmU ma(jnu.-< is an elongated animal, measuring in length about six 

 times the measurement from the dor al to the ventral surface at its deepest 

 part. It is larger and more massively built than A', r/^.s/.s-. It curves a 

 little dorsally (not (|uite so much as K e/z.svV), is bilaterally symmetrical, and 

 is enclosed ventrally by the concrescence of the edges of the mantle lobes, 

 with the exception of the apertures at the anterior and posterior ends, and 

 a fourth aperture situated nearly at the centre of the ventral surface (the 

 aperture is nearer the posterior than the a.iterior end, w'.iilc in J'J. ensis it 

 lies nearer the posterior end). 



The periostracum passes from the outside of the shell to the edges of 

 the mantle lobes, to which it adheres. 



The pallial muscles form a deep band along the margin of the mantle 

 lobes, and, at the anterior end, encircle the pedal aperture through which the 

 foot is protruded. At the posterior end the muscles assume a nrore 

 elliptical condition, being more coalesced both dorsally and ventrally, and 

 form the siphon containing the afferent and efferent chambers. The ventral 

 portion of the proximal portion of the siphon extends more [posteriorly than 

 in E. ensis. 



The foot projects from nearly the centre of the ventral surface of the 

 animal, and proceeds in an anterior direction. A little anterior to the foot 

 is the mouth, and in front of the mouth, is the very broad anterior adductor 

 muscle. On each side of the visceto-pedal mass are the labial palps, com- 

 mencing between, and passing posteriorly to them, are the two gills, which 

 continue as far as the siphon. The inner sides of the bases of the gills 

 are joined together from the foot for about half their distance, whereas in 

 E. ensin they are not so connected. 



The anus opens from the free portion of tlie rectum, into the cloacal 

 chamber behind the posterior adductor muscle. 



The siphon consists of two separate chambers, the upper one the ex- 

 halent, and the lower one the inhalent. The free portions of the siphonal 

 chambers are very short and separate from each other. Both are encircled 

 with a fringe of tentacles (the tentacles are not so long as in E. ensit!). 



The fourth aperture is an elliptical opening which narrows very much 



