370 MAZATLAN UNIVALVES 
Tablet 1730 contains a fragment, intermediate in form be- 
tween PA. mutans and ?Chrysallida clausiliformis, remarkable 
for the sudden transition, after 4 whirls, from a perfectly 
smooth to a highly sculptured surface. The smooth part 
measures *045 by °023. 
Hab.—-Mazatlan ; 1 sp. off Spondylus ; L’pool Col. 
433. PPALABA ————, sp. ind. (a.) 
Tablet 1731 contains a fragment of a somewhat large shell ; 
the first four whirls swelling and smooth, like PA. mutans; 
then with four whirls sculptured as in Chrysallida, with stout 
radiating ribs decussated with spiral stria. ? May it however 
have belonged to a Nassa. 
Habh.—Mazatlan ; extremely rare, off Spondylus ; L’pool Col. 
434, PALABA — sp. ind. (b.) i 
Tablet 1732 contains a fragment of a strong shell, with 
smooth, prominent, strong, elongated tuberous portion, (the 
first whirls broken) followed by divergent, somewhat rounded 
whirls, cancellated as in Phos. 
Hab.—Mazatlan ; 1 sp. off Spondylus ; L’pool Col. 
Famity OVULID. 
Genus OVULA, Brug. 
Fine. Meth. vol. xv. no. 37.—Phil. Hand. Conch. p. 162. 
Amphiceras, (Gronov.) Gray, Proc. Zool. Soc. 1847, p. 143 :— 
=Amphiperas, Morch. 
Volva (Bolten) H. & A. Ad. Gen. vol. i. p. 272. 
435. OVULA VARIABILIS, C. B. Ad. 
Ovula variabilis, C. B. Ad. Pan. Shells, pp. 31, 304, no. 4. 
(May, 1852.) 
Ovula Californica, Sow. Proc. Zool. Soc. [teste Cuming: ? ubi.] 
This shell closely resembles the Atlantic species, O. unipli- 
eatum, Sow. (S. Carolina), O. aciculare, Zam. (W. Indies) and 
O. subrostratum, Sow. (Honduras). The striz at each end are 
extremely fine, and are rarely traceable over the whole surface. 
The shape is sometimes stunted and broad, sometimes acumin- 
