ir. GASTEROPODA: PROSOBEANCHIA. 



379 



BRANCHIA. Two ctenidia (fig. 373), shell 'wich marginal slit or wiili 

 holes corresponding to an anal notch in the mantle; auricles and ne- 

 phridia paired; heart traversed by intestine. Fissdrellid^, keyhole lim- 

 pets; shell conical, with apical opening. Haliotid^e, abalones; shell 

 weakly spiral, flat, with a series of holes. Halwtis* (fig. 362, B). AZYGO- 



FiG. 3T4.— American Pectmibranch gasteropoda. (From Bmney-Uould.) A, Crepulula 

 fnrnicata; B, Lnfuiia i-incta ; (\ lluonaxsa ohsnleta ; D, Littorina palhata; i-, X,. 

 litorea- F Ur(nalpinx cmerea ; O, Purimra lafiillus : H. Buecinum undatum; 1. 



Lunatia hcriit^ 



but two auricles. Teochid.e, operculum 

 TuRBiNlD.B, top shells; operculum calca- 



BRANCHIA. One ctenidium, 

 horny ; Trochus, liar gar Ha.* 

 reous. Turbo, Phasianella. 



Sub Order II. PECTINIBRANCHIxi (Monotocardia, Ctenobranchia). 

 Ctenidium unipectinate, osphradium well diflferentiated (fig 365), intestine 



