TERTIARY CALCAREOUS ALG^J. 15 



coarser (5 to 20 mm. in diameter vs. 8 to 10 mm.). Rothpletz refers 

 to the thickening of the thallus by a repeated " Ueberwucherung " of 

 the hypothallium a, character that is scarcely noticeable in L. homo- 

 geneum, so far as is shown by the sections thus far obtained. No 

 conceptacles were observed in Lithothamnium tuberosum, so the genus 

 remains in doubt. The cell measurements as given by Giimbel are 

 somewhat less than those obtained from our Liihophyllum homogeneum, 

 while those given by Rothpletz from an " Originalstuck " are somewhat 

 greater. Rothpletz often finds GiimbePs cell measurements too small 

 and he intimates that Giimbel had made some error in calibrating his 

 eye-piece micrometer. 



Lithophyllum (?) molare, new species. 

 (Plate 4, Figures 2 to 4.) 



The following is a description of this species: 



Thallus masses 2 to 4 cm. (and more?) in height, composed of more or less 

 fused or anastomosing flattened branches, these 4 to 10 mm. broad, 3 to 5 mm. 

 thick, molariform or subspatulate, the obtuse, retuse, or sparingly corrugated 

 apices sometimes free for 5 to 10 mm. ; perithallium and medullary hypothallium 

 not clearly differentiated, cells of both in regular layers; cells of medullary 

 hypothallium 20 to 26 ju by 10 to 13 M; perithallium rather obscurely or now 

 and then distinctly zonate, showing occasionally 1 to 4 layers of short cells 

 alternating with a subequal number of layers of long cells, the cells subquad- 

 rate in section, the larger 15 to 18 ju in diameter, often 16 pi high and 13 /u 

 broad, the smaller about 8 n in diameter, often broader than high; concepta- 

 cles unknown. 



From bluff (Oligocene, middle of Antigua formation) on north side 

 of Willoughby Bay, Antigua, T. W. Vaughan, b from station No. 

 6881. Another and evidently different coralline alga (a from station 

 No. 6881), with subterete, intricately intertangled branches 1.5 to 

 3 mm. in diameter, was collected at the same time and place, but the 

 two apparently do not occur intermingled. 



In general form and habit, Lithophyllum (?) molare resembles certain 

 broad-branched forms of the recent Lithophyllum dcedaleum Fosl. & 

 Howe, 1 originally described from Porto Rico, and also, in a less degree, 

 the recent Lithophyllum platyphyllum Fosl., 2 from St. Martin, of the 

 Leeward Islands. It seems, however, to differ from both of these in 

 the thicker, more distinctly zonate perithallium and the relatively 

 shorter and (in section) more quadrate cells. In both L. dcedaleum and 

 L. platyphyllumj the larger cells of the inner perithallium or outer 

 medullary hypothallium (the two tissue-systems commonly blend 



1 Bull. N. Y. Bot. Garden, vol. 4, 1906, p. 133, plates 83, 84, and 85, f. 1. 



8 Goniolithon platyphyllum Fosl., Kgl. Norske Vidensk. Selsk. Skr. 1898, No. 6, p. 13; Lithophyllum 

 platyphyllum Fosl., Kgl. Norske Vidensk. Selsk. Skr. 1900, No. 5, p. 18. As was subsequently 

 recognized by Foslie, this species has nothing to do with L. craspedium and L. africanum, 

 between which it was placed in his "Revised Systematical Survey." 



