274 



American Seashells 



strong, axial ribs, but the last 2 whorls with only numerous fine spiral threads 

 crossed by exceedingly fine growth lines. Aperture elongate, rather ex- 

 panded and a little flaring below. Sinus moderately large and simple. Color 

 cream with yellowish brown maculations. Uncommon from shallow water 

 to 25 fathoms. 



Subclass OPISTHOBRANCHIA 



(Bubble-shells, Pteropods, Sea Slugs) 



Order ONCHIDIATA 



Family ONCHIDIIDAE 



Genus Onchidella Gray 1850 



Without a shell, animal slug-like, low, oval, with two short tentacles 

 or eyestalks at the end of which are the eyes. Mantle entirely covering the 

 back; respiratory, anal and female genital pores at the posterior underside; 

 male pore below the right tentacle and above the sensory lobe. Shallow water 

 to intertidal. Formerly placed in the pulmonates, but now beheved to be an 

 early offshoot of the opisthobranchs. See Freter, 1943. 



EYE 



, SCNSORf L066 



MftNTue 

 CftVVTV OPENING 



PNEflviOSTOMe 



Mfti-e 



OP£NINCi 



BEHIND UOb€ 



'MftNTLC 



CluiPiRV fcCOOve 



Figure 58. Underside of the marine slug, Ojichidella, % inch. 



Onchidella floridana Dall Florida Onchidella 



West coast of Florida, the Lower Keys and Bermuda. 



V2 inch in length, uniform slaty-blue to dark-gray; underside bluish 

 white, with a greenish tinge to the veil. Dorsal surface velvety. Mantle 

 margin with about 1 00 whitish, elongate tubercles. Common along the shore 

 at low tide. Lives in rock crevices in nests, returning home after browsing 

 at low tide. 



Onchidella carpenteri Binney 



Puget Sound to Lower California. 



Carpenter's Onchidella 



