ON THE MORPHOLOGY OF THE CEPHALOUS MOLLUSCA 



style " .in connection with the ahmentary canal, has long been known 

 in the Lamellibranchiata, but it has hitherto been supposed to be con- 

 fined to them. However, in Pteroccras, the pyloric sac contains a very 

 complete style, Plate V. [Plate 20] figs. 16, 17. 



The stomach is a wide somewhat quadrangular cavity. The eso- 

 phagus opens into its left anterior angle, while its pyloric orifice, very 

 close to this, is at the right anterior angle. Behind the pyloric orifice 

 the rounded head of the crystalline style projects from the aperture of 

 the pyloric sac, 7, fig. 16. 



Two wide apertures communicate with the liver, and act as hepatic 

 ducts. 



Several considerable ridges of the gastric membrane rise from the 

 floor of the stomach ; the principal one is next to the cardia, and there 

 is a smaller between the cardia and pylorus. The aperture of the 

 pyloric sac is surrounded by an elevated circular ridge, which is slit 

 towards the pylorus, the left edge of the slit overlapping the right. 

 The end of the style projecting from this orifice is opposed by one or 

 two cartilaginous plates upon the principal elevation. It is only the 

 end of the style which is free ; for the rest of its length {\.\\o or three 

 inches) it lies in the pyloric sac (\, fig. 17), which runs back over the 

 intestine, in the thickness of the left side of the mantle, and terminates 

 by a rounded extremity. 



It seems probable that the " crystalline style " is secreted by the 

 pyloric sac, and that it acts as a gastric plate, assisting in the com- 

 minution of the food, although its transparent and delicate texture 

 would not seem to fit it for the performance of any very important 

 office of this kind. 



Its resemblance in position and structure to the crystalline style of 

 Solen is sufficiently remarkable. 



Renal System. — It has been shown that in the Heteropoda and 

 Pteropoda a " contractile sac " exists, placed so as to be bathed by the 

 blood entering the auricle. It has been hinted that this is a renal 

 organ, and I now proceed to give the reasons for my belief that it is so. 



says he " does not know what to make of h." (Vergleichende Anatomic, p. 312.) This 

 statement is contained in a valuable paper upon the anatomy of the MoUusca, entitled 

 " General Observations on Univalves," by Mr. Charles Collier, Staff-Surgeon at Ce)'lon ; 

 printed in the Edinburgh Xew Philosophical Journal for 1829, p. 231. "There is an organ, 

 the crystalline stiletto, confined erroneously by a celebrated naturalist (Cuvier) to bivalves, 

 which is found in every species of Strombus, in Troc/uis twritus, and a species ( Veiiagiis) of 

 Murex. It is enclosed in a sheath, that passes parallel to and by the side of the cesophagus, 

 to the stomach, into which the stiletto enters, leaving its covering ; that end which lies within 

 the stomach is obtuse, laminated, and fixed by a hook of similar substance to its situation. 

 The upper portion is circular, homogeneous, slightly tapering, transparent, of gelatinous 

 consistence, and resembling somewhat a pistil with its stigma." 



