bloomer: anatomy of certain species op SOLENIDAE. 79 



whole of it is withdrawn into the palHa chamber. The proximal portion of 

 the siphon is short, but of greater depth than that of Tcvjelut^ m/us, while 

 the free portions, though long and muscular, are shorter and thicker than 

 those of the same species Internally they show both longitudinal and fine 

 transverse rib'-ing, but externally only the transverse ribbing. 



There are large siphonal retractor muscles. The foot (fig. i. F.) is 

 massive and of medium length, being longer and of a more uniform depth 

 than in T. nifus. 



The gills reach to the proximal portion of the siphon. The inner sides 

 of their bases are joined together, and divide the exhalent from the inhalent 

 chamber. The teeth of the shell are buried in the viscera about the centre 

 of the dorsal surface. 



Musculafure. — The musculus cruciformis (fig. r, M.C.) is present at 

 the extreme ventral edge of the siphon, but it is not so pronounced as in 

 T. rufus. 



i. PaUial muscles. — The muscles of the pallial edge commence at the 

 anterior adductor muscle as a deep band, and gradually decrease in depth 

 as they proceed posteriorly. The muscles of the siphon are strongly de- 

 veloped, and the siphonal retractor muscles, where they adhere to the valves 

 of the shell, present a large surface. 



The anterior adductor muscle (fig. i, A. A.) is a broad, comparatively 

 long, but shallow muscle, flattened dorsally, and curved ventrally. As in 

 2\ rufus it is divided by the ventral integument passing through it. The 

 muscle is connected anteriorly with the mantle lobes, and posteriorly with 

 the dorsal and ventral integuments. 



The posterior adductor muscle (fig. i, P. A.) is more oval in shape 

 than that of T. rufus, and is joined anteriorly by connective tissue with the 

 bifurcations of the pedis retractor posterior muscle and dorsal integument, 

 and posteriorly with the dorsal integument, the siphon, and the mantle 

 lobes. 



Just below the siphon there are two transverse muscular bands — the 

 musculus cruciformis of Von Ihering (fig. i, M.C), which quickly converge 

 and unite at the centre, the four distal ends after passing through the mantle 

 lobes, are attached to the valves of the shell, thereby resembling the same 

 muscle found in Solecurtus strigillafus, but more particularly that in T. 7~ufus, 

 though on a very much smaller scale that the former, and in not having the 

 posterior portion shortened as in the latter. 



ii. Pf'dal Muscles — The muscles of the foot are strongly developed, and 

 structurally approximate nearer to those of Pharella (CuUellus) orientalis 

 than those of T. rufus. 



The pedis retractor anterior muscles run ventrally inside the longitu- 

 dinal muscles (that is, they are exposed when viewed from the pedal cavity). 

 The free portions are thick and short, and pass dorsally to the shell. There 

 are no bifurcations. 



