﻿HAMUSINA. 



303 



sources of error which are so liable to attach to a name of which such an un- 

 fortunate use has been made. 



All names apart, and simply stating the facts as they are presented to us in 

 the Inferior Oolite of this country, we recognise three sections of sinistral shells, 

 which, by way of a temporary arrangement, we might classify as A, B, and C. 

 It is hardly necessary to say that these inosculate. 



Section A consists of regularly conical forms, more or less turrited ; the shell 

 is thin, and entirely devoid of umbilicus. These we have no difficulty in 

 assigning to Hamusina, and indeed the first specimen on our list I have ventured 

 to identify as a variety of one of the forms named by Gemmellaro. 



Section B corresponds in the main to Scaevola, Gemm. The shells are some- 

 what thicker, and the general character is turbinate rather than trochiform. The 

 spiral angle (measuring in the body-whorl) is more or less concave; the orna- 

 mentation is very rugose, with a tendency to produce varices ; the umbilicus is 

 well developed and tolerably deep. This section subdivides into the Calisto- 

 group and the Leachi-growp, of which the latter is by far the most abundantly 

 represented. These shells form the bulk of the genus Cirrus as subsequently 

 defined. 



Section C consists of subdiscoidal forms of considerable variety, where the 

 tendencies already manifested in Section B attain their maximum. The conical 

 form has entirely disappeared owing to the abortion of the spire, thus making the 

 spiral angle extremely concave, whilst the umbilicus is enormous. These forms 

 may be all gathered under Cirrus nodosus, Sowerby. Some authors seem disposed 

 to restrict the genus Cirrus to this species. I have already pointed out that this 

 is not the original Cirrus nodosus of Sowerby, but it is the " Cirrus nodosus, 

 Sow.," of authors and of collections, being Cirrus nodosus, No. 2, of the author of 

 the ' Mineral Conchology.' 



Accepting Hamusina as a near relative of Cirrus, and regarding Seserola as a 

 synonym of Cirrus in part, I have concluded to arrange the sinistral shells of our 

 Inferior Oolite under the two genera Hamusina and Cirrus. 



Genus — Hamusina, Gemmellaro, 1878. 



Shell thin, sinistral, conical, turrited, tuberculated, without umbilicus. Spire 

 acute; body-whorl externally angular; base subconvex. Aperture circular; 

 columellar side excavated and incrusted; lip simple and somewhat extended laterally. 

 Growth-lines oblique. 



It is difficult to share the opinion of Gemmellaro that Hamusina is related to 



