242 HUGH WATSON. 



excepting Strebelia^; for as a general rule, the lai'ger tlie 

 size of the aperture, the smaller is the size of the shell as a 

 a whole in proportion to that of the animal. 



It is not only in the shell, however, that the Oleacinidae 

 resemble Testacella. In both, a deep cleft in the mantle- 

 edge extends forwards from the respiratory opening beneath 

 the right lip of the shell ; and Simroth has found that in 

 Poiretia this cleft contains an olfactory organ, resembling 

 the similarly situated olfactory organ of Testacella. 

 Poiretia also has small labial feelers, very like those of 

 Testacella. So far as I am aware, the histology of the 

 foot and pedal gland in the Oleacinidfe has not been 

 described ; but, judging from Strebel's figures," the pedal 

 gland lies freely in tlie body-cavity in the more highly 

 specialised members of the family, just as it does in Testa- 

 cella. A jaw is absent in nearly all the Oleacinidse, as in 

 Testacella. We have already seen that the odontophoral 

 muscles in the Oleacinidas are tnore like those of Testa- 

 cella than are the muscles of any other form which has been 

 examined; and I have found that in Euglandina the struc- 

 ture of the odontophoral support agrees exactly with that of 

 Testacella. In most of the Oleacinidte the salivary 

 glands are united, but according to Reymond ^ they are 

 separate in the European genus Poiretia, as in Testacella. 

 This, however, is not a very important character, for, as we 

 have seen, the glands may be separate or united in different 

 species of the same genus. The nervous system in the 

 Oleacinidge is also identical with that of Testacella, all 

 the visceral ganglia remaining separate, although they are 

 sometimes veiy closely aggregated in Euglandina. The 

 similarity of the reproductive system is equally striking. It 

 is true that the receptacular duct of Testacella is shorter 



' See ' Jabresli. Yer. Natui'kunde Wiu'ttemb.,' 1907, vol. Ixiii, pi. ix, 

 fig. 8. 



" 'Beitrag z. Keniitn. d. Faima Mexikan. L.-u. Siisswasser-Concbjlien,' 

 1878, vol. iii. pi. xix. fig. 1. 



•' ' Joiu-ii. de Conchyl..' 1853, vol. iv, pp. 16-29, ■p\. i, fig. 1. 



