﻿GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 



467 



"Fossilizatioii like that of the other Astrorians, and rendermg 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 l:]2, fi.ijs. 3, 3(/; I'late VMi, %»• 2, 3, 3a, 36. 



1863. Aslraea lenins Duncan, Gedl. Sof. London Quart. .Tourn., vol. 19, p. 421, 



pi. 13, tig. 11. . 



1867. Heliaslraea tenuis Duncan, Geol. Soc. London Quart. Jouxn., vol. 24, p. 24. 

 1901. Orhicelln tenuis Vaugitan (port), Geolog. Reiclis Mu.«i. Leiden Samml., ser. 



2, vol. 2, ]). 33. 



This species, as weU as Astraea antiyuensis Duncan, was errone- 

 ously confused with Orhicella Dana. I obtained excellent material 

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

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

 species are given on plate 133, figures 3, 3a, Sb. 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 3a illus- 

 trates the costae and the synapticulae between them. 



The following description is based upon four specimens collected 

 by Ml'. Robert T. Hill at a locality 4 inches west of Lares, Porto. 

 They satisfy in aU particidars 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. 



• ' ■' 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 tlie coraUum. 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 imn.; 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 



