TERTIARY CALCAREOUS ALGJE FROM THE ISLANDS OF 

 ST. BARTHOLOMEW, ANTIGUA, AND ANGUILLA. 



By Marshall A. Howe. 



The present paper contains descriptions and illustrations of the fossil 

 calcareous algae collected in February and March 1914, by Dr. T. W. 

 Vaughan, in the Eocene St. Bartholomew limestone of the island of St. 

 Bartholomew, the middle Oligocene Antigua formation of the island of 

 Antigua, and the upper Oligocene Anguilla formation of the island of 

 Anguilla. 



ALGJE. 



Class RHODOPHYCE^. 



Family CORALLINACEJE. 



Genus ARCILEOLITHOTHAMNIUM Rothpletz. 



Archaeolithothamnium affine, new species. 



(Plate 4, Figure 1; Plate 5.) 



The following is a description of this species : 



Thallus terete or slightly flattened, 3 cm. (or more?) long, 3.5 to 6.0 mm. in 

 diameter (8 mm. at a dichotomy), somewhat divaricately dichotomous, more 

 or less sinuous and nodose, the apices broad and rounded-obtuse or subacute; 

 medullary hypothallium zonate, its cells mostly 16 to 30 n by 8 to 13 ju, transi- 

 tion to the perithallium gradual; perithallium more or less distinctly zonate, 

 its cells 8 to 26 ju by 8 to 13 ju, often about 14 ju high and 12 /x broad; sporangia! 

 sori becoming overgrown and embedded, the sporangial cavities elliptic-oval 

 in longitudinal section, 55 to 78 n high and 27 to 46 n broad. 



In the Carlisle marl pit (Oligocene, lower part of Antigua forma- 

 tion), on slope just above the level of the central plain, Antigua, West 

 Indies, T. W. Vaughan, station No. 6873 (type), February 10, 1914; 

 also at McKinnon's (Oligocene, Antigua formation), Antigua, T. W. 

 Vaughan, No. 6888, March 1914. The Latter of the two specimens 

 is partially embedded, but the former (plate 4) is free. The structure 

 in both is well preserved and ground sections exhibit their structure 

 nearly as well as would be the case with living or recent material. 

 A. affine appears to be closely related to the living A. sibogce A. Web. 

 and Fosl. 1 of the region of the Sulu Archipelago, Borneo, and Celebes, 

 from which it seems to differ in its larger cells, especially of the peri- 

 thallium, which are 8 to 26 p by 8 to 13 /x, while in A. sibogce they were 

 described by Weber and Foslie as 5 to 12 y, by 5 to 8 >; in microtome 



1 Foslie, M., Three new Lithothamnia, Kgl. Norsk. Vidensk. Selsk. Skr., 1901, No. 1, p. 3; Weber- 

 van Bosse, A., and M. Foslie, The Corallinacese of the Siboga Expedition, Siboga Exped. 

 Monog. 61, 1904, p. 41, pi. vn. 



11 



