SUCCINEA. 341 
Succinea undulata, var. carmenensis, Fisch. & Crosse, loc. cit. pp. 657, 658, t. 27. 
figg. 6, 6@.—Mexico, Carmen Island, on the frontier of Tabasco and Yucatan 
(Morelet). 
This shell has a more lengthened spire than the other forms of S. undulata 
described by Fischer and Crosse, one of which is referred by me to S. salleana. 
It differs from S. wndulata (Say), Pfeiffer, in the remarkably narrow form of the 
whole shell. 
Succinea lineata, var. sonorensis, Fisch. & Crosse, loc. cit. p. 662, t. 27. fige. 8, 8a, b.— 
Mexico, in the neighbourhood of the Yaqui River in Sonora (Dr. #. Palmer). 
Also a rather narrow form; it wants the spiral (revolving) lines which are 
characteristic of S. lineata, Binney, from Nebraska, and from which that species 
has got its name. The outline of Fischer and Crosse’s figure also differs con- 
siderably from that given by Binney (Terr. air-breath. Moll. N. Am. v. p. 420, 
fig. 208) and by Tryon (Am. Journ. Conch. ii. t. 17. fig. 16). Binney, however, 
mentions Sonora among the localities for S. lineata. 
Succinea cingulata, Forbes, P. Z. S. 1850, p. 56, t. 9. fig. 8 (description copied by Pfr. 
Monog. Helic. Vivent. iii. p. 17, and Fisch. & Crosse, Miss. Scient. Mex., Mollusca, 
i. p. 661).—MeExico, Mazatlan (Capt. Kellett, on the Voyage of the ‘ Herald’). 
The original figure looks very unlike a species of this genus; and Fischer and 
Crosse have suggested that S. cingulata may be a young specimen of some 
Bulimulus. Ei. Smith, however, who has examined the type specimen in the 
British Museum, informs me that in his opinion it belongs to Limnea. 
For Succinea obliqua and S. aurea, mentioned by Fischer and Crosse (loc. cit.), see 
S. undulata and S. pueblensis. 
Fam. ARIONIDZ. 
Shell reduced in size, not covering the whole animal, or internal, or wanting; mantle 
not covering the whole animal. Jaw and radula as in the family Aulacognatha, 
antea, p. 126. 
For the purpose of easier determination I shall treat together all the Stylommatophora 
without shell, or with the shell not covering the whole animal, arranging them in the 
natural families Arionide, Limacide, and Veronicellide, but giving a Comparative 
Table of the genera occurring in Mexico and Central America, based upon the degree 
of development of the shell and the extension of the mantle. The genus Onchidium 
is included for comparison in the Table, but it will be placed at the end of the 
volume, among the submarine mollusca, it being strictly confined to the sea-coast. 
