NUDIBEANCHIATA OF THE L.M.B.C. DISTRICT. 149 



In Ancula m^^afa the lateral ridge has almost disappeared 

 as a ridge, but it is evident that the five pairs of large 

 simple cerata placed at the sides of the branchiae (fig. 10) 

 correspond to the similar structures seen in Polycera and 

 IdaUa. Then in Triopa claviyer (fig. 12) the cerata have 

 become more numerous (seven pairs), are directed more 

 laterally, and extend from the head nearly to the posterior 

 end of the body. 



In passing next to the family Tritoniidae we find that 

 the cerata become branched in an arborescent manner, but 

 on comparing sections of Goniodoris (fig. 6) or Polycera 

 (fig. 9) with those of Candiella jAeheia (fig. 13) it is im- 

 possible to doubt that one is dealing wdth the same series 

 of projections. Cahrilla occidental is, which has been lately 

 described and figured by Fewkes,* presents an interesting 

 intermediate condition between Triopa and Tritonia. Cah- 

 rilla is evidently referable to the Doridoe ; it has short 

 laminated rhinophores and a posteriorly-placed circle 

 of branchiae, but is possessed of six or seven pairs of 

 laterally-placed cerata which are branched at their ends, 

 and are evidently comparable with the parieto-cerata of 

 Tritonia and Dendroiiotus. In Dendronotus the large parieto- 

 cerata become very complicated in form (fig. 14), but are 

 evidently merely a further development of the smaller but 

 similar processes of Candiella or Tritonia. 



Finally, in the great group Cladohepatica we find large 

 and conspicuous hepato-cerata (PI. VI. figs 15 and 16), as 

 in Doto, Eolis, and Proctonotus, but we must regard these 

 as being merely cerata, originally like those of the Doridae 

 and Tritoniidae, wdiich have been invaded by the hepatic 

 caeca and have afterw^ards become enlarged and modified 



* Zoological Exciii-sions, I. Ne^v Invertebrata from California : Boston, 

 89, p. 4-i. 



