336 M. o. A. L. morch's review of the vermetid^. [Nov. 12, 



Indian form Fermetus varians, U'Orb., passing over to the form with 

 plaits ; this form of aperture must consequently be dissolved with 

 age. Varices manieiformes, of Philippi, are not unfrequently met 

 with, the insides of which show several raised transverse laminae, 

 probably arising from the dissolved old whorls. Several species are 

 corroding, but I have never met with a planorbiform corroding 

 shell. 



I divide this genus into the following four subgenera, of which the 

 last two very likely only depend on differences of age, corresponding 

 to Bulla, Marginella, and the adult state of Cyprcea ; but I have 

 not seen a sufficient number of opercula to decide the question with 

 certainty, although I have compared numerous specimens of shells. 

 In the following list of species I use the names Aletes and Thyla- 

 codus, to distinguish the varieties which I regard as analogous. 



Subgenus 1. Vermetus, Adans. 

 T. anfractibus gracilibus, laminis e parietibus procedentibus. 

 Typ. V. Adansonii, Daudin ; V. renisectus, Carp. 



Subgenus 2. Petaloconchus, Lea. 



T. ut prceeedentis, sed laminis ab axi procedentibus. 



Typ. V. macrophragma, Carp. ; cochlidiiim, Carp. ; flavescens. 

 Carp. 



The position of the laminae is not quite constant. In a large dis- 

 sected specimen, where the laminae can be followed throughout the 

 length, they often deviate considerably from the columella. 



Forma 1. Thylacodus, Morch. 



T. ut prcecedentium, sed anf. plerumque longissimi, lami^ris internis 

 nullis ; columella liris spiralibus 4—5, lateralibus obsoletissimis. 



Typ. V. subcancellatus, Biv. ; V. contortus. Carp. , V. conicus. 

 Dill. 



I have seen a specimen of the last species which is in the fore 

 part an Aletes, and in the first whorls a plaited Vermetus. 



Forma 2. Aletes, Carp. 



T. ut prcecedentium, sed anfr. ampli, scep)e sutura dilatata ; colu- 

 mella lira obsoletissima mediana. 



Typ. A. centiquadrus, Val. 

 Vermetus, Adanson. 



Subgen. 1. Vermetus. 



1. Vermetus adansonii, Daudin, 1800. 



" Chaque coquille represente une espece de cylindre de 5 a 6 

 ponces au plus de longueur, dont le diametre, qui a une ligne et demi 

 a deux lignes de largeur en haut, diminue insensiblement jusqu'au 

 sommet, ou elle se termine en une pointe tres-fine ; le nombre des 

 spires varie depuis 5 a 12, peut-etre davantage. L'ouverture s'eleve 



