NO. 2 OSBURN: eastern pacific BRYOZOA — CHEILOSTOMATA 339 



Key to Species of Hippodiplosia 



1. Avicularia present 2 



Avicularia wanting 3 



2. Avicularia usually median and suboral . . . reticulato-punctata 

 Avicularia lateral, usually beside the aperture .... americana 



3. Ovicell radiately ribbed, imperforate insculpta 



Ovicell not ribbed, irregularly perforated pertusa 



Hippodiplosia americana (Verrill), 1875 

 Plate 40, fig. 4 



Lepralia americana Verrill, 1875 : 415. 

 Lepralia americana, Osburn, 1912 :241. 

 Hippodiplosia americana, Hastings, 1930:725. 

 Hippodiplosia americana, Marcus, 1937 :101. 



Zoarium encrusting on shells, sometimes multilaminar. Zooecia mod- 

 erate in size, 0.50 to 0.65 mm long by 0.35 to 0.40 mm wide, quadri- 

 lateral to more or less hexagonal and arranged in quincunx, distinct and 

 ventricose in younger stages. The frontal is a thick tremocyst with large 

 pores ; sometimes rising into a small suboral umbo, and variously rough- 

 ened in full calcification. The aperture is nearly round (slightly quad- 

 rangular), 0.14 to 0.16 mm wide by 0.12 to 0.14 mm long; the poster 

 broadly arcuate between the small cardelles. The peristome is low and 

 thin, without spines, the frontal does not unite with it, especially on the 

 proximal border (a characteristic of the genus). A moderate sized 

 avicularium, with a pointed mandible and complete hinge-bar, is situated 

 near the side of the aperture, directed more or less distally. 



The ovicell is large, about 0.35 mm in either dimension, hyperstomial, 

 prominent, slightly flattened on the upper surface, with numerous pores 

 which are irregular in size, shape and distribution. 



The species is common on the Atlantic coast from Mt. Desert Island, 

 Maine, to North Carolina, especially abundant about southern New 

 England. Marcus recorded it from Santos Bay, Brazil, and Hastings 

 from Balboa, Canal Zone (the only Pacific record). 



Hancock Stations : 254, Agua Verde Bay in the Gulf of California ; 

 253-34, Port Culebra, Costa Rica; 147-34, Tagus Cove, Albermarle 

 Island, and 440, James Island, Galapagos. Depth range 10 to 30 fms. 



