GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 



467 



' ' Fossilization like that of the other Astrorians, and rendering the 

 details indistinct. It is closely allied to the other species of Astroria 

 from Antigua. 



''From the Chert-formation of Antigua. Coll. Geol. Soc." 



CYATHOMORPHA TENUIS (Duncan) Vaughan. 



Plate 132, figs. 3, 3«; Plate 133, figs. 2, 3, 3a, 36. 



1863. Astraea tenuis Duncan, Geol. Soc. London Quart. Journ., vol. 19, p. 421. 



pi. 13, fig. 11, 

 1867. Heliastraea tenuis Duncan, Geol. Soc. London Quart. Journ., vol. 24, p. 24. 

 1901. Orbicella tenuis Vaughan (port). Geolog. Reichs Mus. Leiden Samml., ser. 



2, vol. 2. p. 33. 



This species, as well as Astraea antiguensis Duncan, was errone- 

 ously confused with Orbicella Dana. I obtained excellent material 

 in Antigua, which shows that both the common corallum wall and 

 the corallite walls are synapticulate. Three views of one of these 

 species are given on plate 133, figures 3, 3a, 36. Plate 133, figure 3, 

 is a general view of the upper surface of the corallum; figure 3b shows 

 the synapticulate character of the common wall; and figure 3« illus- 

 trates the costae and the synapticulae between them. 



The following description is based upon four specimens collected 

 by Mr. Robert T. Hill at a locality 4 inches west of Lares, Porto. 

 They satisfy in all particulars Duncan's description of C. tenuis and 

 differ in no important particulars from the Antiguan specimens. 



The corallum is pulvinate, with the calices confined to the upper 

 surface and sides. 



Dimensions 



of specimens of Cyathomorpha tenuis (Duncan \. 



Specimen No. 



Greater 

 diameter. 



Lesser 

 diameter. 



Height. 1 



li 



mm. 

 69 



87 

 100 

 126 



mm . 

 52 

 70 

 100 

 97 



mm . 



55 | Specimen apparently somewhat crashed. 



2 



58 



3 i 



45 Specimen subquadrangalar in shape. 



4 



64 | 







1 Specimens figured. 



The calices of specimen No. 1 (pi. 132, figs. 3, 3a) are described, 

 although those along the top have been somewhat deformed through 

 lateral compression of the corallum. The calices on the upper part 

 of the surface have slightly elevated margins; 0.75 mm. is the maxi- 

 mum height. Some calices are rather deep, about 2 mm.; the 

 diameter of the most nearly circular ones ranges from 3.5 to very 

 slightly more than 4 mm.; the distance between adjacent calices is 

 from a mere dividing ridge to 2 mm.; the calicular edges, however, 

 are usually distinct. Around each calice and joining adjacent ones 

 are equal, acute costae, between which are synapticulae. On the 



