part 3] Jurassic rocks of new- zeala^d. 269 



remainder mostly resemble A. spitiensis var. eoctensa figured 

 in this paper. One of them bears a fossil attached to it that 

 seems to be identical with Placunopsis striatula Zittel. 



AlJCELLA (?) MARSHALL!, sp. UOV. (PI. XIV, figs. 2-4.) 



Description. — Both valves are approximately equal in size and 

 degree of inflation, although the left seems to be slightly the 

 lai'ger of the two. In the left valve, which is well inflated, the 

 beak is rather anteriorly situated, pointed, and projects above the 

 hinge-line. The hinge-line behind the beak is concave ; the hinder 

 margin is produced, more or less rostrate, and rounded in outline ; 

 the lower margin is rather concave, the lower anterior margin 

 rounded, and the anterior margin gently rounded. The surface of 

 the shell is rounded, and has a more or less prominent ridge, which 

 passes from behind the beak to the upper posterior margin, between 

 which and the posterior hinge-line there is generally a concave 

 areal surface. The surface of the shell is smooth, and bears a 

 few narrow irregularly-spaced growth-furrows. 



The right valve is moderately inflated, the beak rather anterior, 

 pointed, and projecting above the hinge-line. The anterior margin 

 is gently rounded, the lower slightby concave ; the posterior margin 

 is narrowly rounded and rather rostrate, the upper posterior 

 margin gently concave. There is a small anterior ear with a deep 

 byssal notch below it. The surface of the shell generally bears a 

 broad shallow median sulcus, and is smooth (except for finely set 

 growth-lines and occasional irregular growth-furrows). The shell 

 is thin and platy in structure. 



Dimensions. — A left valve measures in length 37 mm.; 

 height=24 mm. ; depth = 13 mm. A right valve in length 

 =31 mm. ; height = 24 mm. ; depth = 8 mm. 



Locality. — Five specimens comprising three separate left 

 valves, one right valve, and one with both valves conjoined but 

 rather crushed, were collected by Prof. P. Marshall north of 

 Sanely Bay, half-a-mile south-west of Roaring Bay, south of 

 Nugget Point in the South Island. All are from a bed about 

 3" to 4 feet thick near the middle of the Jurassic sequence. A 

 cast of both valves, rather distorted, 25 mm. long, comes from 

 Kawhia Harbour ; but the exact locality of it is, unfortunately, 

 lost. 



Remarks. — These shells belong to an apparently edentulous 

 bivalve the characters of which are sufficiently obscure ; but 

 it seems to be attributable provisionally to the genus Aucella, 

 on account of the platy structure of the shell and the presence of 

 an auricle in the right valve. The characters of the shape, how- 

 ever, are not those of Aucella, and it is probable that it belongs to 

 a new and undescribed genus which may be rather distantly 

 related to a new genus Iloleoiiuia that I described recently from 

 the Carnic Beds of the New Zealand Trias. The specimens, how- 

 ever, with one or two exceptions, are distorted by crushing, so it 



