GEOLOGY AND PALEONTOLOGY OP THE CANAL ZONE. 391 



Calices slightly elevated, the corallites somewhat swollen below the 

 calicular edges. Diameter, 8.5 to 9.5 mm. Costae prominent; those 

 corresponding to the primary and secondary septa subequal; tertiaries 

 subequal to those of lower cycles or smaller; fourth cycle small but 

 usually recognizable. 



Septa in four cycles, usually differentiated in size according to 

 cycle; primaries and secondaries and occasionally some tertiaries reach 

 the columella. Margins of primaries, secondaries, and tertiaries 

 exsert, up to as much as 1.5 mm., usually about 1 mm.; those of the 

 quaternaries obvious but not prominent. 



Columella rather well developed. 



Locality and geologic occurrence. — The "silex" bed of the Tampa 

 formation, Tampa, Florida. 



Type. — Wagner Free Institute of Science, Philadelphia. 



Paraiype.— No. 324896, U.S.N.M. 



This variety, which intergrades with the typical form of the species, 

 is especially distinguished by its less prominent calices and the better 

 developed last (quaternary) cycle of costae. 



Orbicella tampaensis var. silecensis is near Orbicella costata, from 

 which it is separable especially by the more exsert margins of the 

 primary, secondary, and tertiary septa, and by the quaternary septa 

 having much lower margins than those of the other cycles. The gen- 

 eral resemblance of the Tampa specimens of 0. tampaensis var. silecen- 

 sis is so close to specimens of 0. costata from Anguilla that at one time 

 I thought them referable to the same species, but the differences in 

 the characters of the costae and of the upper septal margins served to 

 separate them. For a comparison of 0. tampaensis with 0. irradians 

 (Milne Edwards and Haime) Vaughan see page 394 of this paper. 



12. ORBICELLA BREVIS (Duncan). 



Plate 97, fig. 1. 



1864. Astraea brevis Duncan, Geol. Soc. London Quart. Journ., vol. 20, p. 37, 



pi. 4, figs. 3a, 3b. 

 1868. Heliastraea brevis Duncan, Geol. Soc. London Quart. Journ., vol. 24, p. 24. 

 1870. Heliastraea brevis Duchassaing, Rev. Zooph. et Spong. Ant., p. 30. 



The following is Duncan's original description: 



Corallum small, irregularly convex above, and slightly concave belcw. Coral- 

 lites short, irregularly distant, and radiating. Calices circular, tolerably elevated, 

 their height varying; the margin is rather sharp, and the external wall is marked 

 by very distinct costae. The septa are very slightly exsert, largest at the wall, arched, 

 the radius of the curve being directed upwards and inwards, passing but a little way 

 inwards before descending abruptly; they- are dentate on the free margin. In six 

 systems of three cycles, with a septum of a fourth in some half -systems; primary 

 septa the largest, the tertiary being small. The laminae are perfect, join the col- 

 umella by ascending processes, and are slightly granular. Costae well developed, 

 passing downwards and outwards from the margin; the primary are equal to the 

 secondary, and there is some variation in the size of the tertiary; they are dentate, 

 37149— 19— Bull. 103 14 



