46 SYNOPSIS OF THE CHARACTERS OF THE 



Patella mucronata. Phil. 



Patella mucronata. Phil. Geol. York. 



Sp. Ch. — Orbicular, depressed, smooth; vertex mucronate, central. 



Professor Pliillips mentions that the base is not plane in this species, but my specimens are too imperfect 

 to ascertain this fact; yet from the mucronate apex, and general form, I have no doubt that they are the same. 

 Diameter eleven lines, height five lines. 



Patella scutieoemis. Phil. 



Patella scutiformis. Phil. Geol. York. 



Sp. Ch. — Shell oval, depressed, smooth; apex acute, inflexed, nearly marginal. 



I have, as yet, seen but very bad specimens of this species, which, nevertheless, seems distinct, by its re- 

 gular elliptical form, and nearly marginal apex. Professor Phillips mentions fine, radiating striae on his speci- 

 men, but they are not visible in the examples I have examined. 



Patella sinuosa. Phil. 



Patella sinuosa. Phil. Geol. York. 



Sp. Ch. — Ovate; anterior end narrower, with a wave or sinus on each side; vertex prominent, one fourth 

 the length of the shell from the anterior end. 



This fine species is chiefly remarkable for the sinuosity on each side, at the anterior end. Length one 

 inch nine lines, width one inch. 



Siphonakia. Sow. 



Gen. Ch. — Patelliform; a siphon, or canal, from the apex to the margin, at one side of the head. 



The lateral siphon of this genus, which distinguishes it from Patella, is not only visible internally, 

 leaving a scar, which interrupts the muscular impression ; but is frequently visible externally, and slightly 

 affects the margin. 



Siphon ARIA Konincki. M'Coy. (PL III. fig. 14). 



Sp. Ch. — Longitudinally oval; width rather more than three-fourths the length, shghtly irregular, apex 

 prominent, obtuse, slightly nearer the anterior than the posterior end, and nearer to the left than the right 

 side ; an obtusely rounded furrow extends from the beak obliquely to the left side of the anterior end ; surface 

 smooth. 



Most nearly alHed to the Patella lateralis, Phil., which is possibly also of this genus ; it differs, however, 

 from that species, in its more lengthened form, obtuse apex, and entirely wanting the posterior radiations. From 

 the Umbrella lavigata, M'Coy, it is distinguished by its large, lateral apex, greater convexity, and anterior, 

 oblique furrow. Length seven lines, width six lines and a half. 



Umbrella. Lam. 

 Gen. Ch. — Suborbicular, patelliform, depressed ; apex nearly central, margin acute; muscular impression 

 continuous. 



Umbrella L^viGATA. M'Coy. (PI. V. fig. 31). 



Sp. C/«.— Ovate, margin sharp, slightly sinuous on each side at the anterior end, apex nearly central ; sur- 

 face smooth, with one or two very obscure concentric undulations. 



From the sharpness of the edge and smoothness of the surface, I think there can be little doubt of this 

 shell being more nearly related to Umbrella than to Patella. The only fossil this runs any risk of being con- 



