GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 3 



substratum alone, but more often developing coarse, irregular 

 rounded excrescences 5-12 mm. in diameter, or short rounded ver- 

 rucae or nodules 2-5 mm. in diameter, the surface in sterile parts 

 mostly smooth, indurated, and occasionally subnitent; hypothallia 

 varying from weakly to strongly developed, 30-170 pt, thick, their 

 cells 17-28 pi by 8-11 \k ; cells of the perithallium in distinct and regu- 

 lar layers except in oldest and youngest parts, the layers in more or 

 less distinct zones, layers of short and of long cells occasionally al- 

 ternating, cells mostly 8-15 [x by 5-8 ix, in decalcified condition sub- 

 moniliate, sphaeroidal to ellipsoidal, 1-2^ times as high as broad, 

 in calcined condition mostly subquadrate or oblong in vertical sec- 

 tion; sporangia superficial, their apicula even with the surface, or 

 slightly protruding, their cavities becoming only imperfectly and 

 irregularly embedded, the sori slightly elevated, very irregular in 

 outline, mostly 0.1-1.0 mm. broad, often widely confluent and anas- 

 tomosing and becoming 5 mm. or more broad, the surface at length 

 whitish and scarious, the ostioles mostly 16-22 \i in diameter, sporan- 

 gia 65-96 [x high (including apiculum), 27-50 \l broad, 4-partite (oc- 

 casionally 2-partite?), the spores irregularly paired or rarely sub- 

 zonate. 



Localities and geologic occurrence. — Covering dead corals, etc., 

 and often forming concretionary pebbles with coral cores, from low- 

 water mark to a depth of several meters, Point Toro, near Colon, 

 Panama Canal Zone, Howe 6832 (type, in Herb. N. Y. Bot. Gard.), 

 January 7, 1910 ; Colon, Howe 6840 (this covers continuously a mass 

 of old coral 32 cm. long and 14 cm. in greatest width) ; also, as a 

 Pleistocene fossil, " from flats near Mount Hope, five feet above tide 

 level," D. F. MacDonald, station 6039, 1 1911. 



Paratopes.— Cat. No. 35298, U.S.N.M. 



In outward form and in its habit of overgrowing old corals, 

 Archaeolithothamniunb episporum resembles A. erythraeum (Eoth- 

 pletz) Foslie, f. durum (Heydrich) Foslie, from the Red Sea and the 

 East Indies, especially as illustrated by Weber- van Bosse and Foslie 

 (Corallinaceae of the Siboga Expedition, pi. 5). Of this species we 

 have seen only one specimen (from near Makassar), communicated 

 by Mme. Weber- van Bosse, but from this and from the descriptions 

 and figures of A. er-ythraeum published by Foslie, Heydrich, and 

 Lemoine, we infer that the Panamanian specimens represent a differ- 

 ent species. Perhaps the most important distinctive character of A. 

 episporwm is to be found in its more superficial sporangia, as may be 

 seen by comparing our photographs (pi. 2, fig. 1; pi. 3) with Hey- 

 drich's figure 2 of a vertical section through a sporangial sorus of his 



1 This is associated with minor amounts of other crustaeeous corallines, including 

 Lithophyllum, species, and Goniolithon, species. 



2 Ber. Deuts. Bot. Ges., vol. 15, p. 68, fig. 2. 1897. 



