NO. 3 OSBURN : EASTERN PACIFIC BRYOZOA CYCLOSTOMATA 753 



Immergentia calif ornica Silen, 1946 

 Plate 80, fig. 7 



Immergentia calif ornica Silen, 1946:6. 

 Immergentia californica, Soule, 1950:364. 



The specimens of /. californica in the Hancock collection are identical 

 in all important respects with the paratype material generously donated 

 by Dr. Lars Silen. The zoaria have the zoids arranged in straight rows, 

 with lateral rows branching to the sides at rather irregular intervals. 

 In length the zoids range between 0.32 and 0.34 mm, and in width the 

 range is from 0.08 to 0.09 mm. The tentacle number is 10 as determined 

 by serial sections. 



This species was originally described by Silen from material collected 

 at Pacific Grove, California. 



Specimens in the Hancock collection are from San Pedro and Portu- 

 guese Bend, southern California. All intertidal. 



Family Penetrantiidae Silen, 1946 



Zoaria with septate stolons. Zoids joined to the main stolons by 

 means of short lateral stolons entering the zoids near the distal ex- 

 tremity. Zoids have a double cuticle and are provided with an operculum. 

 The polypide has a gizzard. Reproductive zoids, the gonozoids, have 

 rudimentary polypides and bear large ovoid embryo chambers. 



Genus PENETRANTIA Silen, 1946 



Zoaria are imbedded in the shells of both living and dead mollusks 

 and cirripeds. The zoids are connected by thin septate stolons. From 

 a primary stolon a short thin lateral branch enters the zoid laterally at 

 the distal end. A zoid modified for reproduction, the gonozoid, is present. 

 The zoids are operculated. The polypide is provided with a gizzard. 

 Genotype: Penetrantia densa Silen, 1946. 



Penetrantia densa Silen, 1946 

 Plate 80, fig. 8 



Penetrantia densa Silen, 1946:2. 

 Penetrantia densa, Soule, 1950:360. 



The zoaria characteristically have the zooecial openings crowded 

 closely together. These openings in the molluscan shells vary in shape 

 from circular to strongly oval. The primary stolons are serrated upon 



