212 RUMINA. 



tooth, and tricuspid laterals. The marginal teeth are formed 

 by suppression of the entocone, being thus bicuspid. 



The eggs are globular, white, and about 2.5 mm. diam. 



Distribution, Mediterranean region, in Europe, Asia and 

 Africa. 



This genus is apparently related to Homorus and to the 

 tropical American Stenogyra (S. obeliscus, etc.), with both of 

 which it agrees in the structure of the embryonic shell and in 

 dentition. The soft anatomy of Homorus, the large Steno- 

 gyras and Riebeckia is not sufficiently known for any exact 

 comparisons. Rumina is undoubtedly a genus of African 

 origin. Where it occurs, it lives in profusion, so that the 

 absence of so conspicuous a snail from European tertiary de- 

 posits seems to signify a geologically recent advent of the 

 genus in Europe. 



With the normal Achatinoid musculature of the penis, 

 Rumina has not the penial complications of Achatina and its 

 immediate relatives. 



R. DECOLLATA (Linne). Plate 53; pi. 55, fig. 99. 



Shell narrowly rimate, cylindric or cylindric-tapering, 

 truncate and closed by a spiral convex plug at the summit; 

 rather thin, glossy, pale flesh-tinted or whitish, the young 

 light brown. Surface irregularly striate, distinctly so below 

 the suture, more or less malleate, and usually showing some 

 spiral lines of vertical punctures. 4 to 6 whorls usually re- 

 main in adult ; they are but slightly convex. Aperture ovate, 

 the outer lip simple, more or less thickened within ; columella 

 vertical, nearly straight, its edge reflexed above, almost clos- 

 ing the minute umbilical crevice. Length 30, diam. 11-12 mm. 



Entire Mediterranean region, the typical forms from south- 

 ern France, Italy, Sicily, Canary Is. Introduced in the 

 Azores, Madeira and Cape Yerde Is., Bermuda, Santo Do- 

 mingo, Cuba (Havana), Charleston, South Carolina. 



Helix decollata L., Syst. Nat. (10), p. 773. Bulimus decol- 

 latus BRUG., Encycl. Meth., i, p. 326. PFEIFFER, Monogr. 

 Hel. Viv., ii, 152 ; iii, 397 ; iv, 456 ; vi, 94 ; viii, 130. LOWE, 

 Journ. Linn. Soc., v, 1861, p. 202, with var. l&vigata and var. 



