WATSON : AFFINITIES OF PYRAMIDULA, ETC. 23 



Pupillidse, and should in my opinion be united with the family, 

 although forming another distinct sub-family within the Pupillidae.^ 

 Ena agrees closely with the Pupillidee in its nervous system, excretory 

 organs, retractor muscles, etc. There is no constant difference 

 between the shells of the two groups, as is shown, for example, 

 by the want of agreement among conchologists as to whether 

 LeucocMloides (or Pupoides) should be placed in the Pupillidae or in 

 the Enidse. The radulse are of the same type, the only difference 

 being that which is usually found between the larger and smaller 

 species of the same group, namely, a tendency for the number of 

 the cusps and the breadth of the teeth to be reduced in most of the 

 Paleearctic Enidse, as compared with the smaller Pupillidae. The 

 reproductive organs also are similar in most respects. The prostate 

 gland, it is true, is longer in the Enidae than in the majority of 

 the Pupillidae, but it is not longer than in Patulastra halmei (pi. I, 

 fig. 2). The only constant difference seems to be that in the 

 Palaearctic Enidae the receptacular duct bears a diverticulum. But 

 this feature can hardly be considered a sufficient reason for regarding 

 the Enidae as an entirely distinct family, since we may find in a 

 single family some genera with, and some without, such a diver- 

 ticulum as, for example, in the Helicidae. And this difference is far 

 less than that which sometimes exists between the reproductive 

 organs of different individuals of Vallonia costata, living together 

 on the same hedge-bank. 



Moreover, the southern forms (such as Pachnodus) that are usually 

 placed in the Enidae are without this diverticulum of the receptacular 

 duct. But these southern genera differ from the Palaearctic Enidae 

 in other respects also. Thus, most of the teeth of the radula, instead 

 of having their major axes practically in a line with one another, 

 are placed more or less obliquely, so that the outer side of one tooth 

 is in front of the inner side of the tooth next beyond. This character, 

 which gives a strikingly different aspect to the radula in many 

 of the southern forms, is entirely absent in the Palaearctic species. 

 There can be little doubt, in fact, that Pachnodus and its allies 

 should be placed in a separate sub-family from the Palaearctic forms, 

 or perhaps even in a distinct family. 



Cochlico'pa is in many ways intermediate between the Valloniinae 

 and the Eninae in its anatomy. The radula, with its small central 

 teeth, is, on the whole, very like that of Vallonia and Patulastra. 

 The prostate gland is chiefly confined to the posterior end of the 

 common duct, as in Vallonia, Acanthinida, and the more typical 

 members of the Pupillidae, although a few tubules are developed 

 further forward. On the other hand, the receptacular duct bears 

 a diverticulum, as in the Enina3, and the penial retractor is not 



^ Hesse is also of the opinion that the Enidae and the Puj)illid8e should be 

 united in one family (Nachr. Deutsch. Malak. Gesell., vol. xlvii^ 1915, p. 57). 



