698 APPENDIX L 
beak salient and incurved ; lower margin arcuate. Exterior surface concentrically striate. 
Anterior part about one-third the whole length.—Length 73 inches; height $2, L. ; thick- 
ness 56°, L., or § H. Apical angle 105°.—Plate 6, fig. 7, shell, natural size; a, outline 
of transverse section ; 8, 8 a, another smaller specimen. 
Wollongong Point, District of Illawarra. 
This and the following species are similar in the regular convexity of the lateral sur- 
face, showing nothing (not even in the cast) of the compression or excavation of the 
sides along an oblique area, belonging to the several preceding species. It is also re- 
markable for its salient incurved beak, a characteristic laid down for our genus Cleobis. 
The M. gigas is similar in this respect. 
Cleobis grandis, Exped. Foss., Amer. Jour. Sci., ii. Ser., iv. 154. 
Pachydomus globosus [?], Morris and M’Coy. 
44, Monta Graciiis (Dana).—Near M. grandis, but having the anterior part about 
two-fifths the whole length, and a larger apical angle. Length 2-9 inches; height 7%, 
L. ; thickness ;5,5 L.; apical angle 125°.—Plate 7, figure 1 a, 0, c, different views, natural 
size. 
Wollongong Point, District of Illawarra. 
Cleobis gracilis, Exped. Foss., Amer. Jour. Sci., il. Ser., iv. 154. 
45. Mmonta? recta (Dana).—Moderately thick; very inequilateral, oblong, sides 
a little compressed, but not at all excavate ; postero-dorsal portion dilated; inferior and 
superior margins nearly straight at middle and parallel, posterior arcuate, anterior ob- 
liquely truncate. Lateral surface concentrically and strongly marked with strie of 
growth, nearly smooth.—Length 3% inches; height ~°5 L.; thickness #5 L. or 75 H. 
—Plate 7, figure 2. 
Wollongong Point, District of [lawarra. 
The straight lines of growth over the medio-lateral surface and straight medio-inferior 
margin, parallel with the dorsal, give a peculiar character to this species. 
Cleobis recta, Exped. Foss., Amer. Jour. Sci., 11. Ser., iv. 154. 
46. Nucuta aprurpra (Dana).—Thick; much elongate; beaks prominent and in- 
flated ; diminishing rapidly behind the beaks and prolonged posteriorly and subacuminate ; 
lower margin arcuate, front narrow arcuate. Cast with a broad flat cardinal area, cari- 
nate externally and nearly at right angles with the lateral surface; general surface 
smooth; muscular impressions excavate, smooth, the posterior overlapping the carina 
in the cast, and quite prominent at the upper extremity; palleal impression a smooth 
faint excavation.—Length 1} inches; height £°, L.; thickness about 475 L., or 3 H.; 
apical angle about 135°; height across the upper part of posterior muscular impression 
about half the greatest height.—Plate 7, fig. 3, cast, natural size ; 3 a, posterior muscular 
impression. 
Wollongong Point, District of Illawarra. 
The specimen is an internal cast, and shows finely the numerous tecth of the hinge. 
The palleal impression is about 14 lines from the inferior margin. There are a few faint 
rays on the surface of the cast, visible in certain lights, 
Nucula abrupta, Exped. Foss., Amer. Jour. Sci., il. Ser., iv. 157, 
