294 MANUAL OF ZOOLOGY. 



The flexure of the intestine is neural, and the sexes are united 

 in the same individual. 



The Pulmonifera include the ordinary land -snails, slugs, 

 pond - snails, &c., and are usually provided with a well- 

 developed shell, though this may be rudimentary (as in the 

 slugs), or even wanting. Though formed to breathe air di- 

 rectly, many of the members of this sub-class are capable of 

 inhabiting fresh water. They are divided into two sections as 

 follows : 



Section I. Inoperculata. Animal not provided with an oper- 

 culum to close the shell. In this section are included the families 

 Helicida (Land-snails), Limacidce (Slugs), Oncidiadcz, Limnceidcv 

 (Pond-snails), and Atiriculidce. 



Section II. Operculata. Shell closed by an operculum. In 

 this section are included the families Cyckstomida and 

 Aciculidcs. 



SYNOPSIS OF THE FAMILIES OF THE GASTEROPODA. 

 (AFTER WOODWARD.) 



SECTION A. BRANCHIFERA. Respiration aquatic, by the walls of the 



mantle-cavity, or by branchiae. 



ORDER I. PROSOBRANCHIATA. The branchiae situated (proson) in ad- 

 vance of the heart. 



Division a. Siphonostomata. Margin of the shell-aperture notched or 

 produced into a canal. 



Fam. I. Strombidtz. Shell with an expanded lip, deeply notched 

 near the canal. Operculum claw-shaped. Foot narrow, adapted 

 for leaping. 111. Gen. Strombus, Pteroceras. 



Fam. 2. Muricida. Shell with a straight anterior canal, the aper- 

 ture entire posteriorly. Foot broad. 111. Gen. Murex, Triton, 

 Pyrula, Fustis. 



Fam. 3. Buccinidce. Shell notched anteriorly, or with the canal 

 abruptly reflected, producing a kind of varix on the front of the 

 shell. 111. Gen. Buccinum, Nassa, Purpura, Cassis, Harpa, Oliva. 



Fam. 4. Conidcz. Shell inversely conical, with a long narrow aper- 

 ture, the outer lip notched at or near the suture. Operculum 

 minute, lamellar. 111. Gen. Conus, Pleurotoma. 



Fam. 5. Volutida. Shell turreted or convolute, the aperture notched 

 in front ; the columella obliquely plaited. No operculum. Foot 

 very large ; mantle often reflected over the shell. 111. Gen. Valuta, 

 Mitra, Marginella. 



Fam. 6. Cypraidce. Shell convolute, enamelled ; spire concealed, 

 aperture narrow, channelled at each end. Outer lip thin in the 

 young shell, but thickened and inflected in the adult. Foot 

 broad ; mantle forming lobes which meet over the back of the 

 shell. 111. Gen. Cypr&a, Ovulum. 



Division b. Holostomata. Margin of the shell- aperture "entire," rarely 

 notched or produced into a canal. 



Fam. i. A r aticidcE. Shell globular, of few whorls, with a small spire, 

 outer lip acute, pillar often callous. Foot very large ; mantle- 

 lobes hiding more or less of the shell. Gen. Natica, Sigaretus. 



