536 GASTROPODA. [Opiathobranchiti. 



Animal having an elongated head-shield, arched and auriculate 

 in front, deeply divided behind, the two processes produced over the 

 shell ; it is brownish above, yellow below. Eyes black and very dis- 

 tinct, in the middle of a small disc. Foot rounded, somewhat cordi- 

 form, with brown striae, and margined with black in front. (Q. & G.) 



Type in the British Museum. 



#a,6. Bay of Islands (Q. & G.) ; Auckland Harbour (H. S.). 



Remarks. This subspecies differs from B. australis in the colour, 

 which is always much more reddish, and adult specimens from Auck- 

 land Harbour are not marbled ; it is considerably more solid, and the 

 fine spiral striation is obsolete or absent. In my opinion, it cannot 

 take the rank of a distinct species. The type was collected by Dr. 

 Stanger. 



Fam. ACERID.33, Pilsbry, em. 

 Bullidce, Fischer (in part). 



Radula having many longitudinal rows of teeth, the central tooth 

 narrow, hardly larger than the laterals, with the cusp serrate ; laterals 

 falcate, with the cusp long and serrate, becoming simple on the outer 

 teeth. 



Shell oval or cylindrical, thin and fragile, of a light yellow-brown 

 or green tint, the spire low or concealed. 



Subfam. ACERIN.E. 



Animal with long narrow head-disc, large epipodial lobes reflexed 

 over the shell, and many cartilaginous stomach-plates. 



Shell fragile, elastic, with entirely exposed nearly level spire, deep 

 sutural slit, and wide anal fascicle. 



Genus 1. ACERA, 0. F. Miiller, em. 1776. 



Akera, Mull., Zool. Danicae, Prodr., 242. Type : A. bullata, Miill. Aceras, 

 Locard. Eucampe, Leach, 1847. 



Animal not completely retractile ; head-disc depressed, long and 

 narrow, truncated in front, tapering behind ; eyes lateral, distinct. 

 Mantle rudimentary, enclosed in the shell, having a posterior fleshy 

 lobe passing backward and ascending the spire in the anal fascicle. 

 Foot long and narrow ; parapodial lobes very large, reflexed over the 

 shell. Stomach containing about a dozen subtriangular, pointed, 

 large and small cartilaginous plates. Jaw separate, oval, reticulated. 

 Radula having the central tooth subtriangular, with bilobed base and 

 reflexed serrate cusp. Inner laterals falcate, with long serrate cusps ; 

 outwardly the cusps become longer and gradually lose the serration, 

 the outer teeth being acicular. 



Shell ovate or oval-cylindric, thin, fragile, elastic, with exposed 

 nearly level spire of several whorls ; last whorl acutely keeled at the 

 shoulder, the keel bounding a flat anal fascicle ; aperture nearly as 



