TROCHOCEEATID^. 
31 
Trochoceras subquadratum, Foord. 
Fig. 3. 
Trochoceras siibquadridiirn. — a, lateral view ; 6, front view, showing the slight 
asymmetry of the whorls. Drawn from a specimen in the Collection. 
Natural size. 
Sp. Char. The asymmetry of the whorls in this species is very 
slight, though quite perceptible ; about If- whorls are seen. The 
rate of tapering is rapid, the shell increasing its diameter about 
three times for each volution. The section is subquadrate. The 
septa are moderately distant from each other, being about 2 lines 
apart on the sides of tlie shell, where the ventro-dorsal diameter of 
the latter is about 9 lines. The ornaments consist of prominent, 
acute aunulations which bend obliquely backwards on the sides of 
the shell, and form a broad and rather deep sinus on the convex 
border. The siphuncle is not seen, nor is the test preserved. 
Remcirlcs. This species is most nearly allied to Trochoceras 
miranclum, Barr. (Syst. Sil. de la Boheme, 1867, vol. ii. pt. i. p. 108, 
pi. xvi. ff. 1-4), from which it is, however, distinguished by its 
more rapid rate of increase, and by the greater distance separating 
the ribs. 
