1890.] NATURAL SCIENCES OF PHILADELl'IlIA. 805 



itself more particularly on the plane of the frond, and is but rarely 

 marginal. 



It seems to me likely that certain special conditions of the envi- 

 ronment are directly instrumental in bringing about some of those 

 modifications in outline which have been held to be of specific 

 value; but if such is the case, I was unable in the present instance 

 to determine any governing cause. In the Bermudas I thought that 

 the crowding of the calyces on one side of the stem of Ocalina was 

 due to the action of local currents, or to one-sided deposit of shore- 

 sediment ; and I believe that a similar observation, or one much in 

 harmony with it, has been made in the case of certain digitate species 

 of madrepore. 

 Porites furcata, Lam. 



A number of individuals of this species were found washed up on 

 the shingle banks of the Isla Verde and of Sacrificios Island. The 

 frequency of fragments shows that the species must be abundant, 

 but we failed to find the exact locality of its occurrence. Not un- 

 likely it is in the vvaters of Anegada Reef 



Porites astraeoides, Lesueur. 



Abundant among the more massive corals of the inner waters. 

 Siderastrsea galaxea, Ellis and Solandt-r. 



Several specimens obtained in the inner waters; also washed up 

 on the beach of the Isla Verde. 

 Orbicella annularis, Lam. 



I identify with this form several rolled or worn fragments, whose 

 partially obliterated characters do not, perhaps, allow of absolute 

 specific determination. This is one of the common forms in the 

 Vera Cruz walls. 



I suspect that several of the generally recognized species of 

 Orbicella are only varietal types, but the material at my command 

 does not permit me to determine this point with positiveness. The 

 specific characters are drawn in very close limits, and I doubt if 

 they can be made applicable to a large series of individuals of any one 

 group. We dredged undoubted specimens of the Orbicella annularis 

 — at least of the form figured as such by Pourtales in his report on 

 the Florida corals — off the coast of Yucatan, near Progreso, in about 

 20 feet of water. The ccenenchyma is of a brilliant vermilion color. 

 Neither Dana nor Milne-Edwards mentions the color of the animal, 

 21 



