NO. 2 OSBURN: eastern pacific BRYOZOA CHEILOSTOMATA 355 



Hippoporidra janthina (Smitt), 1873 

 Plate 45, figs. 13-15 



Lepralia janthina Smitt, 1873 :63. 

 Lepr alia janthina, Osburn, 1914:213. 

 Hippotrema janthina, Canu and Bassler, 1928 :141. 

 Hippotrema janthina, Oshurn, 1940:454; 1947:43. 



The zoarium usually encrusts gastropod shells, rising into rough 

 prominences and subcylindrical branches, the ectocyst varying in color 

 from white in the young to the deep violet color which is suggested in 

 the name of the species. The zooecia are small, 0.30 to 0.40 mm long 

 in the procumbent marginal ones. The frontal is a thick pleurocyst 

 with large areolar pores and usually with a second row of pores ; the 

 pleurocyst arises as a series of costal ridges between the areolar pores 

 and spreads upward to the aperture, carrying the openings of the pores 

 upward at the same time, which often gives the frontal the appearance 

 of a tremocyst ; the ridges unite proximal to the aperture to form an 

 irregular umbonate process. The aperture is a little elongate, about 

 0.11 by 0.09 mm, the anter rounded back to the strong cardelles between 

 which the poster extends in a broad arch ; the row of areolar pores 

 extends around the distal end of the aperture. The primary peristome 

 is low, thin and smooth, without spines; in advanced calcification the 

 frontal may cover the primary peristome with a rough, slightly raised 

 wall on which pointed tubercles are occasionally present. The oper- 

 culum has the form of the aperture, indented on each side at the level 

 of the cardelles, well chitinized and yellowish in color. Small pointed 

 avicularia, much elevated, are usually present on the front, and rarely 

 there are larger interzooecial avicularia with a longer mandible. 



The ovicells are prominent at first, not closed by the operculum, 

 with a rounded frontal area which may become covered by secondary 

 calcification. 



The species is common in the Gulf of Mexico, where it was described 

 by Smitt and where it has been recorded by Osburn and by Canu and 

 Bassler. It has not hitherto been noted on the Pacific coast. 



Hancock Stations: 1071-40, San Felipe Bay; 1078-40, Tepoca Bay; 

 283, San Pedro Nolasco Island; and one colony (without other data) 

 from Conception Bay, all from the Gulf of California between 26° 

 and 31° N. Lat., at 2 to 60 fms; also 2196, at Cabeza Ballena, near the 

 extreme tip of the peninsula of Lower California, 30 fms. 



