20 
MUSEUM BULLETIN No. 31. 
Horizon and Locality . Rather common in the lowest feeds of the 
Trenton (Lorette) at Montreal (near corner Christopher Columbus 
and Bellechasse streets, Mile End), and in the Lower Trenton (Glens 
Rails) at Crown Point, N.Y. 
Platystrophia minuta sp. nov. 
Plate VI, figure 10. 
Several specimens of this small shell have been collected, but all 
except one are brachial valves. These indicate a small biconvex shell, 
almost circular in outline, with a short hinge and sharp, narrow fold 
and sinus. The fold shows two plications which bifurcate about mid- 
way, thus producing four at the front. This is the typical American 
method of introduction of plications, so that these specimens cannot be 
regarded as the young of the last species ( P . champlannensis) . The 
sinus of the single pedicle valve shows only a single plication. It is, 
however, a very small shell, and the adult undoubtedly had three. 
There are four plications on each side of the fold ion the brachial 
valve, and five on each side of the sinus of the opposite one. The 
holotype (brachial valve) is 6 mm. long, and 7 mm. wide ; the paratype 
(pedicle valve) is 4-5 mm. long and 5 mm, wide. 
Comings figured a shell from Prof. Schucherfs collection 1 which 
probably belongs to this species. This specimen was from Montreal 
and though the exact horizon and locality are unknown, Oumings was 
probably correct in surmising that’ it came from the lower 10 feet of 
the Trenton. He says of his specimen, which is 5 mm. long, that 
there are “but four to seven plications on the slopes ; the shell is nar- 
rowest at the hinge line, and considerably less transverse than the 
Trenton Palls type (the index is 1*23 in the specimen figured, which 
is about an average individual). The second and third plications of 
the sinus arise about 4 mm. from the beak.” 
The writer has not met with this species at Montreal, hut from 
the occurrence at Lorette, there is every reason to believe that it 
occurs in the quarries at Mile End. 
Platystrophia minuta differs from other .American species of the 
genus in its very small size, and the late appearance of the secondary 
plications in the fold and sinus, as well as in the small number on the 
sides of the shell. 
Horizon and Locality. Known definitely only from the lowest 
Trenton (Lorette) in the gorge at Lorette, Que., where the types were 
-collected by E. J. Whittaker. 
iAm. Jour. Sc., 15', 19'0-3, p. 22, fig. 9. 
