Orbicella altissima -39- 
irregular in their arrangement* There are six systems, and in 
most of them there are three cycles ?*ith or without a part of a 
fourth in one-half of the system, so that there are constantly 
six septa in a system instead of eight. The endotheca is well 
developed; and the dissepiments are close, stout, and nearly 
horizontally parallel. The exotheca is abundant, forming small 
cells with arched outlines. Height of corallum 6-8 inches. 
Diameter of calices 2/l0 inch. 
Locality . — -St. Croix, Trinidad." 
Gregory— places Duncan's Hel iast raea alt i ssima in the synonymy 
1 J Quart. Jour. Geol. Soc. London, vol. LI, p. 272, 1895. 
of Orbicella acropora (Linn.), without stating why. He may be right, 
but the calices are large for 0_. acrop ora (here called £. annular i s ) 
and the presence of quaternary septa make it probable that it is dis- 
tinct. According to Duncan's figure every other septum reaches the 
columella, a septal arrangement which is one of the characteristics 
of 0. annular! s . I did not see the type in London, and think that 
until it is restudied or additional material has been collected at 
the type locality it will not be possible to reach a positive de- 
cision as to the validity of the species. 
