590 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Measurements in mm.—Holotype, length 9.4, brachial length 9.5, midwidth 
6.6, anterior width 9.8, thickness 6.2. 
Type.—Holotype: 117172. 
Horizon and locality —Table Head series in Newfoundland: At Table Point. 
Discussion——This species is broadly triangular and is marked along the an- 
terior third by a few strong costae. The valves are also subequal in depth and 
both are moderately compressed. The species is unlike J. costata in outline and 
ornamentation ; it is different from J. paucicostata in having the costae extend 
nearly to the middle. 
IDIOSTROPHIA sp. 1 
Plate 113, A, figures 1-5 
Shell small, elongate triangular; posterolateral margins nearly straight, form- 
ing an apical angle of 55°; greatest width at the front. Valves moderately con- 
vex in lateral profile; brachial valve slightly deeper than the pedicle valve. Sur- 
face smooth except at the anterior margin which is costate; 5 costae mark the 
pedicle valve and 4 the brachial valve. Median costa on pedicle valve opposing 
a median sulcus on brachial valve, both narrow. Brachial valve marked by a faint 
depressed line from beak to median depression. Both valves with median septa, 
that of the brachial valve being the longer. 
Measurements in mm.—66308a, length 5.5, brachial length 5.3, width 4.4, 
thickness 2.9. 
Figured specimens.—66308a,b. 
Horizon and locality. —Boulder in Mystic conglomerate in Quebec, Canada: 
In Range 6, Lot 20, Stanbridge Township. 
Discussion.—These specimens are the smallest ones of Jdiostrophia known, 
but they may represent the young of some species. Immature characters may be 
seen in the fact that the odd number of costae is on the pedicle valve while the 
space between the median 2 on the pedicle valve forms an indistinct sulcus. No 
species is available for comparison. 
Genus NEOSTROPHIA Ulrich and Cooper, 1936 
Neostrophia Utricu and Cooper, Journ. Paleont., vol. 10, No. 7, p. 631, 1936; Geol. Soc. 
Amer. Special Pap. 13, p. 252, 1938. 
NEOSTROPHIA ? GREGARIA Cooper, new species 
Plate 120, A, figures 1-6 
Shell small, subpentagonal to subcircular in outline, length and width about 
equal. Beak obtuse ; greatest width generally at about the middle; sides rounded. 
Surface smooth. 
Pedicle valve gently convex and with the greatest convexity in the umbonal 
region. Umbo somewhat narrowly swollen; sulcus originating at about the mid- 
dle or slightly posterior to it, widening rapidly to occupy more than half the 
width, shallow and ending in a short, narrowly rounded tongue. Ridges bound- 
