GASTEROPODA. : 285 
lines. South Seas (= Echinospira, Krohn and Jasonilla- 
-Maed). 
Recluzia, Petit, 1853. R. Jehennei, Red Sea. R. Rollandiana, 
Atlantic, and Mazatlan. 
Animal pelagic, resembling ianthina; one inch long. 
Shell paludiniform, thin, with a brown epidermis; whorls 
ventricose; aperture ovate-oblique, slightly effused at the base, 
margins disunited; inner lip oblique, rather sinuated in the 
middle; outer lip acute, entire. 
These so-called genera, formerly thought to belong to the 
Atlantide, are, for the most part, composed of prosobranchiate 
larvee; but the genera to which they belong has not yet been 
ascertained. 
ORDER IT.—PULMONIFERA. 
THIS order embraces all the land-snails and other mollusca 
which breathe air. They are normal gasteropods, having a 
broad foot, and usually a large spiral shell; their breathing- 
organ is the simplest form of lung, and is like the branchial 
chamber of the sea-snails, but lined with a network of 
respiratory vessels. One large division of the land-snails is 
furnished with an operculated shell; the rest are in-operculate, 
and sometimes sheli-less. 
The pulmonifera are closely related to the plant-eating sea- 
snails (holostomata), through Cyclostoma, and to the nudibranchs 
by Oncidiwm. As a group, they are generally inferior to the 
sea-snails, on account of the comparative imperfection of their 
senses, and the union of the functions of both sexes in each 
individual. 
SEcTION A.—IN-OPERCULATA. 
The typical pulmonifera vary much in appearance and habits, 
but agree essentially in structure. Most of them have suffi- 
ciently large shells; in the slugs, however, the shell is small 
and concealed, or rarely quite wanting. Snail-shells contain a 
larger proportion of animal matter than sea-shells, and their 
structure is less distinctly stratified (p. 32). In form these 
shells represent many marine genera. The greater part are 
terrestrial, only some of the smaller families inhabit fresh 
waters or damp places near the sea. The respiratory orifice is 
small and yalye-like,* to prevent too rapid desiccation in the 
land-snails, and to guard against the entry of water in the 
* Hence they are called Adelo-pneumona (concealed-lunged) by Gray. 
