97 Buda Limestone, Whitney 13 



Holectypus planatus Cragin, 1893, Geol. Survey Texas Fourth Ann. Report 



pp. 159, 160. 

 Holectypus planatus Hill, 1901, U. S. Geol. Survey Twenty-first Ann. 



Report, pt. 7, p. 226. 

 Holectypus planatus Clark, 19 15, U. S. Geol. Survey, Monograph, Vol. 



LIV, pp. 65, 66, PI. XXV, figs. 2a-f, 3a-c, 4, PI. XXVI, figs. ia-e. 

 Dimensions. — Diameter, 14 mm.; height, 7.25 mm.; peris- 

 tome, 4.5 mm.; apical system, 1.5 mm. 



Description. — Test small, subcircular; upper surface ele- 

 vated, inflated; lower surface flattened or concave toward the 

 peristome. 



The ambulacral areas are narrow, straight, widest at the ambi- 

 tus, and somewhat lanceolate in form. There appear to be six 

 rows of tubercles at the ambitus, but they decrease in number to- 

 ward the peristome and apical disk. 



The pores are uniserial, small, and round. 

 The interambulacral areas are a little more than twice as 

 wide as the ambulacral areas. There are six rows of tubercles 

 at the ambitus, but this number rapidly decreases toward the 

 peristome and apical system. 



The apical disk is small and regular in outline. It consists 

 of five genital plates perforated by large genital pores, and five 

 ocular plates. The madreporite is large and occupies the central 

 portion of the system. 



The peristome is a little less than one-third of the diameter 

 of the test. It is slightly notched and decagonal in outline. 



The periproct is oval and extends from the peristome to the 

 outer margin of the test. 



There are only two specimens at hand and they are so poorly 

 preserved that it is very difficult to make a satisfactory determina- 

 tion or description of them. They probably belong to the species 

 H. planatus, but there is some possibility that well preserved 

 specimens would show that they do not. 



Number of specimens: 4. 



Occurrence: Buda Limestone, Austin, Texas. 



