GASTEROPODA. 73 



and Sutton. Possibly in the interval the shell may have undergone a slight change. 

 Both forms of the shell, with the denticulations well shown, are not uncommon in the 

 Middle Glacial of Billockby, but I have not seen it from either the Chillesford bed or the 

 Lower Glacial sand. 



Rissoa senecta, 8. Wood. Supplement, Tab. V, fig. 15. 



Locality. Cor. Crag, Sutton. 



Length, yjjth of an inch. 



A single specimen of this genus, shown in the figure above referred to, has lately been 

 found by myself, which I cannot refer to a known species, and I have therefore given to 

 it provisionally the above name. The volutions (about five) are nearly flat ; the costae 

 few (ten or eleven), large, coarse, and wrinkled ; suture distinct, but not deep ; spiral 

 striae large and distant ; body whorl two thirds the length of the shell ; aperture large 

 and ovate. 



Rissoa reticulata? Mont. Crag Moll., vol. i, p. 103, Tab. XI, fig. 5. 



In the ' Crag Mollusca ' I referred this shell to R. reticulata, Mont., with a doubt. 



Dr. Homes makes this Crag shell identical with R. Montagui, Payr., and in the list in 

 Mr. Prestwich's Coralline Crag paper Mr. Jeffreys refers the Crag shell to " R. calathus, P. 

 and EL, not R. reticulata, Mont./' while in his 'Brit. Conch.,' vol. iv, p. 12, he says 

 calathus is but a very doubtful species, and in his view only a variety of R. reticulata ; 

 and then adds (p. 13) that S. Wood's Crag shell called reticulata more resembles calathus 

 than reticulata, and may be an intermediate variety. In this chaos of opinion I have 

 thought it wisest to retain my shell under the designation given to it in the ' Crag Mol- 

 lusca,' and with the same doubt. 



Rissoa Stefanisi, Jeffreys. Crag Moll., vol. i, p. 106, Tab. XI, fig. 12 (as R. 



costulata, S. Wood). 



Rissoa Stefanisi, Jeff. Brit. Conch., vol. iv, p. 36. 



This shell was described by me in the ' Crag Mollusca ' as a new species in ignorance 

 that the name was preoccupied for other shells, as has been pointed out by Mr. Jeffreys 

 in vol. iv, p. 36, of 'Brit. Conch.,' who there proposed for it the name Stefanisi. This 

 name I have therefore adopted. 



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