GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 393 



same thickness as the septa; occasionally a rudimentary costa is 

 seen, and is not represented by a septum. The exotheca is inclined 

 and abundant. The endotheca is very abundant and inclined. 



" Diameter of corallites (costae not included) four-tenths inch [10 

 mm.]. 



"Loc. Antiguan Tertiary deposits. 



"The large size of the corallites, the low septal number, the long 

 septa and costae, with the small columella and highly developed 

 endotheca, distinguish this species." 



One of Duncan's original specimens, in the Geological Society of 

 London, is represented by plate 98, figure 1. 



I did not obtain in Antigua any coral definitely referable to 0. 

 insignis. 



Regarding the specimens from Serro Colorado, Arube, referred by 

 me to Orbicella cavernosa , l the following notes will be made (see 

 pi. 98, fig. 2, 2a) : 



The corallites are circular in cross section, and have a diameter 

 of a centimeter, sometimes slightly greater. The distance between 

 them is 3 mm. or even greater. Endotheca and exotheca are very 

 richly developed. The septa are usually 24 in number, alternately 

 larger and smaller, all of the larger reach the columella; occasional 

 small quaternaries. They are thin, but are thickened at the wall 

 sufficiently to form a so-called "pseudotheca." There are two speci- 

 mens of this coral from Serro Colorado, one of which is completely 

 siiicified, and a large portion of the other has undergone silicification. 

 The columella is lax, spongy, and fairly large, occupying about one- 

 third of the diameter of the corallite cavity. These specimens closely 

 resemble Duncan's Astraea radiata var. intermedia, but have larger 

 corallites; they are very near 0. costata (Duncan), from which they 

 differ by having thicker and fewer septa and a larger columella; 

 O.antillarum differs by its somewhat smaller corallites; I discover 

 no difference from 0. insignis Duncan. 



14. ORBICELLA INTERMEDIA (Duncan). 



Plate 97, fig. 2. 

 1863. Astreea radiata var. intermedia Duncan, Geol. Sec. London Quart. Journ., 

 vol. 19, p. 421. 

 Astraea radiata var. intermedia Duncan is, according to its original 

 description, characterized by "having the thircl cycle of septa com- 

 plete, and a little excess of vesicular endotheca. * * * The 

 variety forms a link between the great astraeans of the Miocene of 

 the Antilles and the existing Astraea radiata of the Caribbean Sea, 

 Astraea antillarum being closely allied to it." The type-specimen, 

 No. 2943, Geological Society of London, is represented by plate 97, 

 figure 2. The diameter of the corallites is about 5 mm., distance 

 between corallites from 1 to 2 mm. There are in places indications 



i Geclog. Reichs. Mus. Leiden Samml., ser. 2, vol. 2, pp. 32-33, 1901. 



