NO. 1 DURHAM, BARNARD: EASTERN PACIFIC STONY CORALS 27 



The next intermediate is like the previous in branching form but the 

 verrucae are still smaller (up to 3 mm), less elongated, and more per- 

 pendicular to the surface of the corallum. The intercalicular spinules are 

 slightly coarser with a tendency toward tufted ends. Columella and septa 

 as in preceding variation. 



The next intergrade has slightly smaller and more irregularly 

 developed verrucae which resemble nodules. The branches are very 

 flattened, stout, and short, forming close hemispherical clumps. These 

 specimens have the appearance of being rejuvenated or very old, with 

 massive, dead, worn bases. The columella is larger and styliform with 

 the directive ridge less evident; twelve septal ridges are present. The 

 intercalicular spinules vary from moderately slender and tufted to broad- 

 ly flattened with very spinose ends. 



The last variation noted consists of specimens with terete bases, and 

 massive, flattened branches with nodular, perpendicular evenly spaced 

 verrucae slightly larger than in the preceding variety (up to 4 mm in 

 length). The intercalicular spinules are very broad and clavate, the ends 

 greatly spinose, with gradations down to shorter, pointed granules. The 

 directive ridge varies from low and narrow to massive and wide. A styli- 

 form columellar spinule may project from this ridge. Septa when evident 

 are 6 in number. This form resembles P. elegans Dana. 



The variation in this species ranges from the prominent verrucae of 

 the typical members to the smallest verrucae of type number 4, with the 

 verrucae of type number 5 slightly inflated and more even. The inter- 

 calicular spinules range from slender with simple tips to broadly flattened 

 with lacerated and granular ends. 



Specimens from Sta. 638-37 have been deformed by the gall-crab 

 Hapolocacnus marsupialis Stimpson. Schmitt ( 1936, Expls. and Field- 

 Work Smithson. Inst, in 1935, pp. 34-36, fig. 36) reports the occurrence 

 of this crab on corals at Sta. 414-35 (Port Utria, Colombia). The gall- 

 crabs have altered the symmetry of P. robusta considerably, producing 

 leaf-like projections and large galls which completely enclose the crabs 

 except for a line of perforations where two projections have fused. 



The variety pumila of P. robusta is differentiated by its mode of 

 growth due to regeneration of the colony. The colony branches exhibit a 

 nodular and clavate growth form, the verrucae becoming fewer and 

 enlarging into globose branchlets. (PI. 1, fig. 6) 



The forms of Pocillopora robusta resemble several Hawaiian and 

 Indo-Pacific species and eventually they may be found to be identical 

 with one or more of these. 



