304 MOLLUSCA. 
most countries the genus Physa is inferior to Limnwa in species and individuals, as 
well as in size; but in Mexico and Central America Physa is equal or even superior 
to Limnea in these respects. Also in Australia the presumed Physw exceed by far 
the Limnee. 
Concerning the name Bulinus, see the note under the subgenus Aplecta. 
Subgen. APLECTA. 
Aplexa, Fleming, Hist. Brit. Anim. p. 276 (1828) ; Beck, Index Moll. p. 116 (1837). 
Aplecta (emend.), Hermannsen, Ind. gen. Malac. i. p. 65 (1846); Fischer & Crosse, Miss. Scient. 
Mex., Mollusca, ii. p. 83 (nec Guenée, 1835). 
Bulinus (Adanson), H. & A. Adams, Gen. Moll. ii. p. 239 (1858) ; Binney, Land and Freshw. Shells 
N. Am. ii. p. 97. 
Shell acutely ovate or fusiform, very glossy, smooth or with faint vertical ridges, of 
a deep orange or brown colour, sometimes with pale vertical streaks; columellar 
margin of the aperture comparatively short and thick. In the living animal the edges 
of the mantle are plain, and only a little or not at all extended beyond the margins of 
the aperture (see Strebel, Beitr. Mex. Land- und Siissw.-Conch. i. t. 6. fig. 25 infra). 
This subgenus, the type of which is the European P. hypnorum, is now by most 
authors regarded as a distinct genus, on account of the want of digitaticns or indenta- 
tions in the edges of the mantle*. The form of the radula, which I have examined 
in some Mexican species, is, however, quite like that of the typical Physw, and the 
differences in the shell are so vague and indistinct that, without a knowledge of the 
living animal, it is often impossible to say whether a species belongs to Aplecta or to 
Physa (see also my remarks under the subgenus Stenophysa). 
In Mexico and Central America the subgenus Aplecta is represented by more 
numerous and larger species than in any other part of the world. 
Bulinus, Adanson, is probably an Jsidora, a genus which differs essentially from 
Physa, including Aplecta, in the very different form of the radula [see Jickeli, Land- 
und Siissw.-Moll. N.Ost-Afr. p. 200, t. 3. figg. 2-4 (1874)]. Moreover, Adanson’s 
name is ante-Linnean, his work having been published in 1757, a year before the 
introduction of the regular binomial nomenclature in the tenth edition of Linné’s 
‘Systema Nature’; and, further, Adanson’s nomenclature differs from the Linnean, as 
he uses the names of species as distinct simple words, quite independent of those of 
the genus, just as Buffon did the French names of animals. 
# 
1. Physa maugerez. (Tab. XIX. fig. 20.) 
Aplexa maugerie, Gray, Beck, Index Moll. p. 116 (1837) (sine descr.)’; P. Carpenter, Catalogue 
of Mazatlan Shells in Brit. Mus. p. 180 (1857) °. 
Physa maugere, Woodw. Manual of the Mollusca, p. 171 (1851-56) *; Sowerby, in Reeve’s Conch. 
* dm\exros, not braided, plaited, or entwined. 
