22 STUDIES ON AUSTRALIAN MOLLUSCA, 



With this species I have completed the work of figuring the 

 unfigured shells of the Chevert Expedition. Rhytida jamesi, 

 Brazier (P.L.S.N.S.W. i., 1876, p. 99) is now regarded by its 

 author as s3^nonymous with B. franklandiensis, Forbes. This 

 decision, in which I concur, makes a figure of it needless. 



The Genus Ctiloceras. 



(Plate ii., figs. 28, 29, 30.) 



The name Ctiloceras was proposed by Watson* for a remark- 

 able shell taken in Torres Straits. Whether the shell is adult, 

 and to what group it belongs, are unknown. Watson suggested 

 that it was related to Ccecnm, and yet included it among Vermetus. 



A larger series than Watson studied has come into my hands, 

 and it aj)pears that several species of Ctiloceras occur. Although 

 I regard Ctiloceras as an immature state comparable to Simisigera, 

 possibly the young of species already named, yet it seems con- 

 venient to appl}^ provisional names to the different forms. 



For comparison a mutilated example of C. cyclicitm, Watson, is 

 shown at fig. 28. It is 1*6 mm. in major diameter, and was 

 found by Mr. J. Brazier in Torres Straits at the depth of 8 

 fathoms. 



Taken by the same collector in the same localit}^ is a shell 

 shown at fig. 30 which measures 1-54 mm. in major diameter. 

 It is at once separable by its clathrate sculpture. I propose to 

 call it Ctiloceras dathratum. 



Another and more advanced form, shown at fig. 29, I name 

 Ctiloceras striatum. In this the nucleus is more prostrate than in" 

 the others, the first spiral whorl is more tightly coiled, leaving a 

 smaller orifice; the radiating sculpture is weak and distant; close 

 fine spiral grooves ornament the shell. In the example drawn 

 there are one and one half spiral whorls. The aperture is rather 

 Ijroadly reflected. There is no evidence to show whether this 

 feature indicates maturit}^ or the approach of a third stage in 



* Watson, Reports Chall. Exped. xv., p. 465, pi. xxi. f. I. 



