CLAUSILIA. 303 



as the uterus, and more than double its thickness. The recepta- 

 culum seminis is an oval pedunculated gland, lying either along 

 the uterus, or obliquely across the body, a short distance below 

 the hermaphrodite opening, enveloped in soft tissue. It is pro- 

 vided with a long appendage, attached along the uterus, and equal 

 in length to it. This appendage contains an orange coloured, 

 tough flagellum, filled with a whitisli substance, and possibly 

 represents the arrow (or armatorial) sac. 



" I have not observed the presence of spermatozoa in the so- 

 called ' receptaculum seminis ' ; it was tilled with flattened 

 transparent bodies and some colouring matter. The vas deferens 

 branches off about half way from the uterus, makes a few twists, 

 attaches itself to the tissue just below the hermaphrodite opening, 

 and then shortly after becomes thickened, being at this place 

 fixed with a small and thin retractile muscle. The penis makes 

 three distinct twists, or almost coils ; it is very long and the 

 terminal half is more thickened than the other ; it ends with a 

 thin flagelhmi. 



" The jaw is semilunar, narrow, thin, concentrically very finely 

 and radiately distantly and indistinctly, striated, the anterior 

 concave edge is nearly perfectly entire. 



" The radula is long, moderately narrow, consisting of about 80 

 transverse, slightly angular series of teeth, there being 53 teeth in 

 each series. The centre tooth is smaller than the adjoining, with 

 a simple, inflected and pointed tip ; it is contracted towards the 

 base. The 14 inner laterals are longer and stronger than the 12 

 outer laterals. They are all tri-cuspid ; at first the median cusp 

 is by far the largest, gradually the lateral increase in size, 

 while at the same time the median cusp decreases, until on the 

 outermost lateral teeth, the three cusps are almost equal. On 

 the whole the form of the teeth agrees better with that of the 

 Helicid^ than with the Zoxitid.i:. The dental formula is 12 + 

 14_1_14+12." (StoUczka.) 



The characteristic and peculiar feature of the present genus— - 

 the clausilium — has been described by several auMiors. The first 

 to draw attention to it appears to be Daubenton * who referred 

 to it as an " opercule a ressort." Miiiler t was tlie next to give a 

 short description of it under Helix [^ClausiUci] hidens, but more 

 elaborate accounts were given by J. 8. Miller J, l)r. Gi-av §, 

 Caillaud '; and Fischer^, the latter two elucidating their observ- 

 ations with figures. Finally a lucid description, illustrated bv 

 elaborate figures, bv E. A. Smith and B. 13. Woodward ** will be 



* Hist, et Mem. Acad. Soi. Paris, 1743. p. 47. 



t Verm. Terr. Fluv. ii. 1774, p. 117. 



+ Ann. Philos. n. s., iii, 1822, p. 378. 



§ Zool. Journ. i, 1824, p. 212. 



II Jouru. Conchyl. iv. 1853, p. 420, pi. 13. figs. 1-4. 



•I Man. Conchvl. 1883, pp. 484, 48.5. figs. 251-255. 



** Ann. Mag. Nat. Hist. ser. 6, r, 1890, p. 209. 



