GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 7 



the alternation of layers of short and long perithallic cells, or by the 

 interpolation of reduced secondary hypothallia ; the larger perithallic 

 cells mostly 13-Q2 {/, by 11-14 pi., usually higher than broad, the 

 smaller subquadrate, about 8 p. square, or sometimes much compressed 

 (7 \l high, 14 p. broad) ; conceptacles becoming embedded; tetrasporic 

 conceptacles much flattened, oblong or elliptic-oblong in radio-ver- 

 tical section, the cavity 500-740 p. in maximum width, 130-230 p. in 

 height ; roof of the tetrasporic conceptacle rather sharply defined, its 

 cells in regular vertical rows of 1-4 cells, often elongate vertically, 

 becoming sometimes 25-30 p. high. 



Locality and geologic occurrence. — Oligocene, Culebra formation, 

 "about half way between Monte Lirio and Bohio Ridge, on the relo- 

 cated line of the Panama Railroad," collected by D. F. MacDonald 

 and T. W. Vaughan, 1911 (station No. 6026). 



Holotype and paratopes.— Oat. Nos. 35299, 35300, U.S.N.M. 



The specimens obtained are more or less embedded in a hard rock 

 matrix, so that our photograph (fig. 1, pi. 7) can give only an imper- 

 fect idea of the outward form of the plant. With a little mental 

 clearing away of the matrix, it seems probable that in size and ex- 

 ternal appearance, the species may be compared with rather coarse 

 eroded conditions of the living Lithothamnium glaciale Kjellman, 

 but there is little similarity in structure; the perithallic cells of L«. 

 vaughanii average considerably larger than those of L. glaciale and 

 they are arranged in more distinct layers; the embedded tetrasporic 

 conceptacles of L. vaughanii are more flattened than those of L. 

 glaciale, their cavities have about twice the maximum width of those 

 of L. glaciale and the specialized character of the conceptacle roof 

 is not noticeable in L. glaciale. 



In external habit Lithothamnium vaughanii may perhaps be com- 

 pared also with the living Lithophyllum racemus (Lamarck) Foslie 

 forma crassum (Philippi) Foslie 1 of the Mediterranean and Ad- 

 riatic seas, especially as shown in Hauck's figure 2 2 under the name 

 Lithothamnium crassum Philippi, though the Panamanian fossil 

 sometimes develops longer and perhaps more flattened branches than 

 this form. 



Of the living Lithothamnieae now known to the present writer as 

 occurring in the West Indian region, Lithothamnium vaughanii per- 



^Kgl. Norske Vidensk. Selsk. Skr., 1898, pt. 3, p. 9, 1898. Foslie's identification of 

 Lithothamnium crassum Philippi as a form of Lithophyllum racemus (Lamarck) Foslie 

 was accepted by Heydrich (Bot. Jahrb., vol. 23, p. 536, 1901), but Mme. Lemoine quotes 

 Lithothamnium crassum Philippi as a synonym of Lithothamnium calcareum (Pallas) 

 Areschoug. It is not, however, apparent that any of these writers examined authentic 

 material of Philippi's Lithothamnium crassum, if such exists. It is of some interest, also, 

 to note that less than six months before Heydrich accepted Lithothamnium crassum 

 Philippi as a form of Lithophyllum racemus he named it a« the type of a proposed new- 

 genus Stichospora (Ber. Deuts. Bot. Ges., vol. 18, p. 316, 1900). 



2 Hauck, F. Die Meeresalgen Deutschlands und Oesterreichs. In Rabenhorst, L.„ 

 Kryptogamen-Flora von Deutschland, Oesterreich und der Schweiz, vol. 2, pi. 1, 1885. 



