126 TOURNAL OF CONCHOLOGY, VOL. 9, NO. 4, OCTOBER, 1898. 



R. zetlandica in shape and sculpture, but the outer lip is not expanded. 

 Both the latter species, according to Monterosato, have been confused 

 by writers under the synonym R. dathrata Phil., while the oblong 

 form of R. calathus is var. constricta Mtros. 



Another form of R. calathus — dwarf, conical, and short spired — 

 from Scilly and Freshwater West, resembles R. stibcalathus Mtros. 

 from the Canaries; but the apex of the latter is more pointed and the 

 aperture smaller. Mr. G. B. Sowerby says that R. fenestrata Krauss, 

 from South Africa, "differs very slightly from R. calathus" and that 

 he is "induced to think it a variety." 



R. reticulata Mont. — Every part of our coasts, from the Scilly 

 Isles to the Shetlands. 



As remarked in treating of R. calathus, it cannot be separated from 

 this species either as regards shape or sculpture. If specimens from 

 different localities are examined the variations will be found bewilder- 

 ing. Sometimes the longitudinal, and at other times the spiral 

 sculpture predominates, and sometimes the penultimate is coarser 

 than the last whorl, or vice-versa (the four and six spirals mostly 

 depended on by collectors to define the two species being an unreli- 

 able test, especially in the dwarf or male); the length of the spire also 

 varies; and as to shape the forms are endless. After an examination 

 of thousands of specimens from many localities and depths, I cannot 

 define a single character that will separate the two as specific. The 

 only safe separation that can be made for the purpose of classification 

 is that where the shell is conical, the penultimate whorl has four spirals, 

 and the longitudinal ribs prevail over the spirals, they may be called 

 R. calathus. 



I have not found R. reticulata in any of the Channel Islands, and 

 it is rare at Scilly; but both districts supply a "missing link'' which 

 may be ascribed either to this or to R. calathus. It is of the same 

 oblong shape as R. reticulata, with the longitudinal ribs partially 

 suppressed, and where the penultimate whorl is finely sculptured, as 

 in that species, the body-whorl has the coarser cancellation of 

 R. calathus, but where the penultimate whorl is the coarser, the body- 

 whorl has the finer sculpture of R reticulata. Undoubtedly some of 

 these "missing links" may be called by either name. 



The colour is sometimes of a uniform brown, and more rarely 

 white. The male or dwarf form is of course equally diffused with the 

 type, and partakes of the same endless variations of shape and 

 sculpture. Many Hebridean examples in collections are really 

 R. calathus, the error chiefly arising from northern specimens of the 

 latter being more finely sculptured than those from the south of 

 England. The finest come from Oban and the Shetlands. 



