198 J. B. S. MOOHE. 



line style which I found in Typhobia and in certain other 

 Tanganyika Gastropods, and more especially the pyloric 

 caecum, in which this style is contained, requires more atten- 

 tion than it has hitherto received. The existence of these 

 structures in connection with the alimentary canal has long 

 been known in the Lamellibranchiata, and it was formerly 

 supposed to be confined to them. It is further well known 

 that in the Lamellibranchiata the style has by no means the 

 same relations in them all. In Anodonta and Mutela it is 

 free in the intestine and not contained in a pyloric caecum as 

 in Lutraria and many other forms, nor is the caecum present 

 in the former types. When, however, the style and the caecum 

 are both present, the latter structure apparently has invariably 

 the relations represented in fig. 53, the caecum being a long 

 stomachic appendiculum. This caecum does not necessarily 

 contain a style, and thus of the Lamellibranchiata it may be 

 said that in some the style has indefinite relations, and there 

 is no pyloric caecum present ; while in others the caecum is 

 present, but does not necessarily contain a style. It was long 

 ago pointed out — first, I believe, by Collier^ in 1829 — that in 

 several Gastropods, the Strombidae, also in species of Trochus 

 and of Murex " there is an organ, the crystalline styletto, 

 confined erroneously by a celebrated naturalist (Cuvier) to 

 the bivalves. It is enclosed in a sheath that passes parallel 

 to and by the side of the oesophagus to the stomach, into 

 which the styletto enters, leaving its coverings." 



This interesting observation was subsequently confirmed 

 and extended by Huxley 2 to Pterocera, and the organ was 

 again more completely described by M. F. Woodward, the 

 relations of the style and caecum to the stomach as this author 

 describes them being shown in fig. 53. Haller^ has confirmed 

 Collier's observation especting the existence of this structure 

 in S trombus, and has extended them to Rostellaria, 

 but he did not recognise the significance of the structure 

 in relation to that of the Lamellibranchs ; nor does he 

 appear to have been aware of Collier's and Huxley's obser- 

 ' Loc. cit. See p. 19U. - Loc. cit. See p. 190. ^ Loc. cit. See p. 190. 



