J. D. MACDONALD ON THE CLASSIFICATION OF THE GASTEROPODA. 79 



example of this genus *, whicli I collected myself on the Wreck Reef, I found that all 

 my previous remarks on its anatomy were correct, save that the lingual membrane was 

 stated to support a " multiserial pavement of minute teeth." Employing a oue-sixth-of-an- 

 inch objective (Ross), I discovered my mistake with regard to this very small strap ; and I 

 think I may now very safely say that it is septiserial ; and so far, indeed, Triforis agrees 

 with CeritUum. But when we take its otoliths, retractile prolwscis, and lateral labial 

 plates (composed of amber-tinted rhomboidal cells) into consideration, a place near Triton 

 or Bcmella can scarcely be denied to it. I am still convinced that the early state of its 

 shell affords only an apparent mark of aflB.nity to Cerithinm. On the other hand, three 

 openings homologous with those of Triforis are strikingly apparent in some BcmellidcB. 



Having made one flagrant mistake, however, with regard to Triforis, I feel now rather 

 disposed to leave the determination of its true status to more able malacologists, thro^v- 

 ing out one hint — that its operculum is pointed, with an apical nucleus, as in Cerithiopsis 

 (Eorbes), which also possesses a retractile proboscis. 



An error of observation is far more unpardonable than the false determination of the 

 genus to which any particular shell may appear to belong ; for it often happens that in 

 the short but indeiinite descriptions of the shell-characters given by authors, perspicuity 

 is sacrificed in the attempt to attain conciseness. On this account I fell into another 

 mistake, confounding a short and stumpy Fasciolaria, having very obscure plates on the 

 pillar, and a crenulated outer lip, with Swainson's Tritonidea, which has now l^ecome 

 synonymous with Fisania. The operculum in both genera is stout and claw-shaped, and 

 the animals themselves are not at all unlike each other. 



The lingual dentition of Fasciolaria, Fusus, and Clavella, liowever, may be at once 

 distinguished from that of Fisania, which I believe to belong properly to the Buccinidce 

 and not to the Muricidce, if the Buccinmn cinctum of Quoy, and Fnsiosterna of Swainson 

 may be taken as true examples. 



So far as I have been able to discover, besides Murex itself, Memifitsns (Sw.) is the 

 only genus, in the whole of the Muricidce, having an operculum with an approach to an 

 apical nucleus, which is essential to Fisania. 



The family-difference observable in the dentition of the Buccinidce, Fusidce, and Muri- 

 cidce is so distinctive, that, when once recognized, no confusion of the species of one family 

 with those of another can possibly occur ; and thus an unfailing guide is afforded in the 

 determination of doubtful cases, which may be more or less conformable with the defini- 

 tion of Fisania or any other ambiguous genus. 



I leave the case of the AciculidcB-f an open question untU I shall have the opportunity 

 of comparing the anatomy of Geomelcmia and Acicula with that of Egea (Benson P), ^A'hich 

 I think may possibly be identical with the former genus ; and if so, it wUl bring along- 

 with it some freshwater and littoral genera, viz., Hydrohia, Syncera, and a number of 

 beautifvil little Faludina-like shells now placed in the Bissoulce. 



Trimcatella is doubtless close at hand, though perhaps sufficiently distinct to form the 



* Having obtained a second dextral Triforis at Moreton Bay, it may be safely stated that tlie shell is not invariablv- 

 sinistral, though commonly supposed to be so by conchologists. 

 f As accepted by Mr. Woodward. 



