COOKE : ON PSEUBOMABOINELLA. 5 



belong to the shell at all. Marginella proper has no operculum ; 

 Pseudomarginella has two different opercula, the one unguiculate, 

 the other horny, with a medio-lateral nucleus, and neither fits 

 the mouth of the shell. (2) The polished surface of the shell of 

 M. glabella is produced, as in Cyprcea, by extensions of the mantle- 

 edge, which overlap and envelop the greater part of the shell. 

 Carriere, in his notes on the anatomy, mentions their existence.^ 

 In the case of both his species of Pseudomarginella, he expressly 

 records that there were no such prolongations of the mantle. But 

 he does not seem to have asked himself how, in that case, the shell 

 happens to carry a high surface-polish. He tells us that the five 

 shells in question lived " in der felsigen Gerollzone nahe am Ufer ", 

 so that they cannot have developed their lustrous surface, as do 

 many species of Oliva, Mitra, Natica, Nassa, etc., by ploughing about 

 in wet sand. In the absence of either of these two conditions, the 

 polish on the shells of Pseudomarginella remainis unexplained. 

 (3) He records, in the case of M. glabella, the fact that the four 

 columella folds of the shell form strong indentations on the internal 

 attachment muscle, as tbey do in all spiral shells furnished with 

 similar folds. Carriere makes no such remark in discussing the 

 anatomy of Pseudomarginella, except to say that the operculum 

 prevented the complete retraction of the shell, and so made the 

 indentations faint. Yet the columella folds continue to the top of 

 the spire, and must have heavily indented any soft portion of a 

 genuine animal which came in contact with them. 



Before \\e can accept observations of the nature contained in 

 these papers, or the theories built upon those observations, ample 

 confirmation and illustration are required ; neither are forthcoming. 

 In the forty years which have since elapsed, nothing even remotely 

 resembling the phenomena here recorded has been detected by 

 observers, whose number has been multiplied by scores. It must 

 follow, beyond a doubt, that in this case the observer was deceived ; 

 some mistake, it is both needless and impossible to determine its 

 exact nature, must have occurred. The name Pseudomarginella 

 must disappear from our catalogue of the mollusca. 



^ " Bei dem lebenden Thiere umhiillt der Mantel mit seinen grossen 

 Seitenlappen die Schale, wodurch die Glatte derselben hervorgerufen wird." 



