Fintay.—New Shells from New Zealand Tertiary Beds. 413 
have at least 50; the type of S. evolutus at a stage comparable to S. chat- 
tonensis has 26. ere are no shorter or closer grooves at first, the . 
transition from the smooth anterior area to strong equidistant grooves 
being abrupt. Grooves oblique in same direction as initially over most 
always posu. inc bod to dorsal margin. АП the grooves are stronger, and 
do not get closer най, but indeed considerably wider apart, and do 
not become weaker. Shell is much flatter, especially anteriorly; medial 
depression not so marked, but valve more flatly depressed postero-dorsally. 
Growth-lines and rest- Ramer are much fainter. 
gth, 16 mm. : height, 7-5 mm.; width (one valve), 1-5 mm. 
E (unique), from “Chatton, near Gore (Waiarekan D, in author’s 
collec 
ШО. the single specimen is juvenile vm Mec it differs 
strikingly man the other two species. The ratio of length to height is 
only 2-13 : 1. The ratio of anterior to posterior ais in the three species 
described may be tabulated as follows 
Species Auge Para 
S. bensoni  .. .. 10mm. 18:5 mm. 1-85 : 1 
S. evolutus .. .. 85mm. 135mm. 19 1 
S. chaltonensis wer T HE 9 mm. po 
Barytellina anomalodonta n. sp. (Plate 50, figs. Ta, 7b, Te.) 
Shell rather small but very thick and solid, in shape like an obliquely 
truncated ellipse, no anterior lateral teeth, right valve with a large posterior 
ое tooth. Beaks contiguous, sharp, but not prominent, dorsally 
tened, directed slightly backwards. Anterior end slightly longer ; 
susti from beaks a regular elliptical eurve is described until nearing 
posterior end, when ventral border inse a slight sinuation due to external 
i 1 
NS antero-dorsal_ edge; it meets комы ventral border at angle of 
and vice versa. External surface appears y ‘first sight smooth and polished, 
but under lens shows roughening due to extremely fine and dense growth- 
lines; there are also very inconspicuous narrow and flattish radial riblets 
. with ‘interstices of quite variable width; these riblets are so little raised 
as to appear more like rays on surface, and, combined with shape of shell, 
give it a superficial resemblarice to dorm “ya perconiusa е _ There 
into a wide and shallow sinuation which oc occupies inost of posterior end 
in right valve but is narrow and subobsolete in the more convex left valve ; 
posterior side it is bounded by a much narrower, cord-like secondary 
fold from which there is a vertical drop m bor straight dorsal margin. 
A flat lanceolate area is thus formed when the valves are in conjunction, 
be & strong resemblance to the cH of a N left 
valve an additional slight fold traverses this area close to ligament, which 
near hinge. Adductor-scars deeply impressed, especially the posterior, 
which is subrhomboidal; the anterior elongated, pyriform.  Pallial sinus 
