44 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 16 



Subgenus Pseudocolumnastraea Yabe and Sugiyama 



Pseudocolmnnastraea Yabe and Sugiyama (1933), Jap. Jour. Geo!., 

 vol. 11, p. 15. 

 Subgenotype: Pseudocolumnastraea yamanarii Yabe and Sugi- 

 yama. 



Pavona (Pseudocolumnastraea) galapagensis 



Durham and Barnard, new species 

 Plate 3, figs. 16a, b 



Corallum massive, forming a moderately large colony rising into 

 several gibbous knobs; corallites circular, ranging in size from slightly 

 less than a millimeter to 2 mm, averaging 1.5 mm; larger corallites on 

 top surface of corallum may be as much as 1 mm apart, mostly less; 

 occasional ones may have confluent or closely appressed thecae ; corallites 

 on lateral surfaces of corallum consistently have closely appressed or 

 confluent thecae; septa 12-20, mostly 12, rather occasionally with 14-16, 

 infrequently with 18-20; half of the septa extend to the columella, the 

 other half extend one-third to one-half the distance to the columella; 

 septal interspaces 2-3 times as wide as thickness of major septa; second- 

 ary septa slightly thinner than primary septa; all septa thicken toward 

 thecal wall; all septa equally exsert (0.5 mm), primary septa with 

 inner edges vertical and top edges flat, septa of secondary system with 

 inner edges oblique and upper edges somewhat rounded, becoming flat 

 if extending far out over peritheca; margins of septa smooth, septal 

 faces with numerous small, pointed granules deep within the calice, 

 septocostae of basal corallites with granular faces; costae extend from 

 calice to calice; occasionally, individual costae from 3 calices meet and 

 fuse tripartitely ; thecal wall consisting of synapticulae between septa; 

 endo- and exothecae well-developed, dissepiments averaging 1 mm apart ; 

 exothecal tabulae slow to develop near surface of corallum, causing a 

 pitted appearance of the peritheca; columella composed of a single, ele- 

 vated contorted piece. Corallites at base of corallum may be elongated 

 and have more septa and more pieces to the columella. 



Remarks: This species is very closely related to Pavona maldivensis 

 (Gardiner) but differs in having about 4 less septa per comparable calice, 

 thinner septa, and a more twisted columella. Gardiner's species is 

 very polj^morphic, exhibiting 3 distinct types of calices, only one of which 

 has the Pseudocolumnasiraea-iorm. The only calices on the new species 

 which do not exhibit synapticulothecae are occasional basal ones, the 

 exothecae of which have filled up, obliterating the separate walls. 



