76 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



cyst, but occasionally this may be replaced by a pair of smaller ones in 

 the proximal corners. Ooecivim prominent, hemispherical, smooth, hyper- 

 stomial and not closed by the operculum. In the presence of the ovicell, 

 the larger avicularium appears to be always absent, but when the smaller 

 avicularia are present one of these is usually located at one side distally 

 and its chamber is not involved in the ooecial cover. Genotype, Mem- 

 branipora spitsbergensis Bidenkap, 1897. 



While definitely a member of the family Alderinidae, the combina- 

 tion of characters presented by M. spitsbergensis will not permit its 

 inclusion in any known genus. 



Bidenkapia spitsbergensis (Bidenkap), 1897 

 Plate 8, fig. 6 



Membranipora spitsbergensis Bidenkap, 1897 :619. 



Membranipora spitsbergensis, Nordgaard, 1900:9. 



Membranipora spitsbergensis, Kluge, 1906:38. 



Callopora spitsbergensis, Nordgaard, 1918:44. 



Callopora spitsbergensis, Oshum, 1919:609; 1923 :8D; 1932:8. 



The zoarium is encrusting but loosely attached or rising in bilaminate 

 or unilaminate frills or flabellate expansions, rough, conspicuous and 

 yellow to orange in color when fresh. 



The zooecia vary much in dimensions but are usually large, averag- 

 ing about 0.80 mm long by 0.45 mm wide, occasionally more than 1. 

 mm in length, and the zooecia are unusually deep. The Myalls are all 

 comparatively thin, the mural rim thin and smooth or granulated, the 

 dorsal wall thin, smooth, shining and thickly punctate with white dots. 

 In the absence of ovicells and avicularia the gymnocyst is usually little 

 developed ; the cryptocyst varies greatly, sometimes filling a third of the 

 proximal end of the opesia and again it is scarcely noticeable. Large 

 multiporous septulae are present, about a third of the distance above the 

 dorsal wall. Spines are entirely wanting. 



Two sizes of avicularia are known. Usually a large one occupies the 

 whole width of the proximal end of the zooecium, the short rostrum ele- 

 vated and the bluntly triangular mandible directed backward or laterally ; 

 frequently this type is wanting and they are never present when an ovi- 

 cell is developed on the preceding zooecium. Instead of the single large 

 avicularium there is sometimes a pair of smaller ones, one in each proxi- 

 mal corner, and one of these is rarely present at the distolateral side of 

 the ovicell. There is some intergradation between the two types of avicu- 

 laria, single median ones occasionally present among the smaller avicu- 



