528 MOLLUSCA 



2. ARIOLIMAX Morch. Body tapering and somewhat keeled: 6 

 species, all on the Pacific slope. 



A. columbianus (Gould). Color greenish-yellow, sometimes blotched 

 with darker patches; length 15 cm.: Washington, Oregon, and Califor- 

 nia, in damp forests. 



A. niger Cooper. Color nearly black, sometimes gray ; length 5 cm. : 

 central California. 



FAMILY 14. PHILOMYCIDAE. 



. Slugs. No internal or external shell; body limaciform, with the 

 mantle covering the entire back and tapering behind; no caudal mucous 

 pore ; ureter reflexed : 2 genera ; 5 American species. 



1. PHILOMYCTTS Ferussac. Jaw 

 smooth, strongly arched and with a 

 median projection ; respiratory pore 



near the head; foot with marginal 

 Fig. 820 Philomychus carolinensis (Bin- 



ney). 1, mantle ; 2, respiratory pore. grooveb. 



P. caroliniensis (Bosc) (Fig. 



820). Color whitish with dark spots and blotches; length 7 cm.: eastern 

 and central states, in forests in trees, under bark, or in rotten wood, being 

 partial to basswood. 



2. PALLIFERA Morse. Jaw with stout ribs on its anterior surface, 

 and without a median projection. 



P. dorsalis (Binney). Color ashy, with an interrupted mid-dorsal 

 line; jaw with 9 ribs; length 18 mm.: northeastern and central states. 



P. hemphilli (Binney). Color black; jaw with 4 or 5 ribs: central 

 states; rare. 



ORDER 3. PROSOBEANCHIATA. (STREPTONEURA.) 



Mostly marine snails, in which the ctenidium lies in the mantle cavity 

 at the forward end of the body (Fig. 828,1) and in front of the heart. 

 In a few primitive forms (Zygobranchiata) a pair of ctenidia is present. 

 The Helicinidae and Proserpinidae are without gills and the ctenidium is 

 replaced by a lung, the animals beng terrestrial. Near the ctenidium 

 in the inner surface of the mantle is the hypobranchial gland, which, 

 in Murex and Purpura, becomes the purple gland; its function is un- 

 known. With rare exceptions the animal is provided with a shell, which 

 is often of large size and is sometimes very thick and heavy, and in 

 many forms very beautifully marked and colored. The operculum is 

 almost invariably present, and is either calcareous or horny, and either 

 spiral or annular. 



