t^^l

146 trifiojfiDiE.
281. Nodularia (Nodularia) involuta (Benson).
Nodidai-ia {Nodtdaria) involuta (JJenson) ; Simpson, Washington,
D.O., Smiths. Inst., Nat. Mus. Proc. xxii, 1900, p. 817.
Unio involutus (Benson), in Hanley, Rec. Biv. Shells, 1856, p. 385,
pi. 23, fig. 19 ; II. & T., C. I. p. 19, pi. 41, fig. 2.
Original description :—Peaked ovate, not so very inequilateral,
compressed in front, swollen in the umbonal region, thin, polished,
rather pale green, very obscurely subradiated ventrally with ochreyellow,
rather tinged with blue dorsally, marked with 2 or 3 dark
green lines on the anterior slope, partially marked with some
close and regular shallow groove-like posterior wrinkles, elsewhere
smooth ; ventral edge strongly arcuated and much rising behind,
less curved yet almost equally rising in front; anterior side
tapering to a blunt subcentral peak, no umbonal ridge; hinder
dorsal edge nearly straight, scarcely sloping; umbones swollen,
prominent, with a few longitudinal corrugations ; beaks incurved;
nacre silvery ; umbonal cavity ample ; lateral teeth large, laminar,
raised, the shorter one very elevated at its extremity.
" In the single specimen ^escribed from, there is no cardinal
tooth, but the hinge-plate is elevated beneath the umbones."
Long. 34, lat. 48 mm.
Hah. Assam.
A curiously thin, smooth, boat-shaped form which is considerably
inflated, the diameter respectively of a right and left valve
in the British Musum Collection being 10-75 and 9-5 mm.
Section EADIATULA.
Madiatula, Simpson, Washington D.O., Smiths. Inst., Nat. Mus.
Proc. xxii, 1900, p. 820.
TrPB, Unto crispisulcatus, Benson ; Burma.
Mange. Burma ; Assam ; Cambodia.
Original description:—Shell rather solid, triangular oval, with
high beaks which are but little inflated, not very full at post base,
bluntly pointed behind, the beaks and entire surface covered with
radiating, occasionally slightly zigzag or divaricate ridges, which
are cut more or less into nodules or cancellations by concentric
sulcations; the sculpture of the posterior slope stronger, and
curving upward; pseudocardinals of the left valve 2 to 3, ragged,
the anterior larger, two in the right valve, with a parallel-sided
socket, the larger teeth compressed but rather solid.
282. Nodularia (Radiatula) crispisulcata {Benson).
Nodularia {Radiatula) crispisulcata (Benson); Simpson, Washington,
D.C., Smiths. Inst., Nat. Mus. Proc. xxii, 1900, p. 820.