1918 | Packard: Molluscan Fauna from San Francisco Bay 289 
Pholadidea penita (Conrad) var. parva (Tryon) 
Penitella parva Tryon (1865), p. 39. 
Pholadidea penita, var. parva, Wood and Raymond (1891), p. 55. 
Description.—This variety was originally described by Tryon (1865) as 
follows: 
‘«Shell small, ovate, inflated, rather thick. Surface divided by an oblique 
impressed rib, posteriorly to which it is concentrically striate, while anteriorly 
it is radiately ribbed. 
The flexed dorsal margins are each covered with a thick irregularly shaped 
accessory valve, with a single central valve posterior to them. The latter is 
somewhat pentagonal, emarginate in front. 
Hiatus filled by a heavy callus, which juts out somewhat into a point or 
beak, instead of preserving a rounded outline.’’ 
Only the typical form of this species was recognized among the 
collections of the Survey. The southern variety was found within 
this region by Wood and Raymond. This form burrows into Haliotis 
shells. 
Range—San Francisco, California (Wood and Raymond); San 
Pedro to Lower California (Dall). 
Martesia Leach Gray 
Martesia intercalata Carpenter 
Martesia intercalata Carpenter (1863), p. 637. 
This small boring mollusk is found on the shell of Haliotis. The 
abalone to protect itself from the intruder secretes nacre, thus forming 
the much prized abalone blister. 
Carpenter (1863) reports this from the Farallon Islands. Since 
no Haliotis was taken by the Survey this species was not found among 
the collections. 
Range—Farallon Islands to Catalina Island, California (Dall). 
Zirfaea Leach 
Zirfaea gabbi Tryon 
Plate 32, figure 1, plate 54 
Zirphaea gabbi Tryon (1863), p. 144, pl. 1. 
Zirphaea crispata Leach, Gabb (1869), p. 52; Wood and Raymond (1891), 
p. 55. 
Description—This species was originally described by Tryon (1863) as 
follows: 
‘‘Shell large transverse, obliquely divided by a deep furrow proceeding 
from the umbonal apex to the basal margin and forming a corresponding rib 
on the internal surface of the valve. Posteriorly to the furrow the shell is 
