10 BULLETIN 103., UNITED STATES NATIONAL MUSEUM. 



enoides, as figured by Kosanoff x and by Lemoine, 2 but the crusts are 

 evidently more massive than in that species. 



Although the outward form of Lithothamnium isthnii is more or 

 less obscured by being embedded in rock, it seems probable that in its 

 typical condition (No. 35301) the external appearance of the plant 

 may be compared with the recent plant from the Adriatic Sea figured 

 by Hauck 3 as " Lithophyllum decussatum Solms," which Foslie * 

 afterwards referred to his Lithothamnhim philippii — a species that 

 he maintained even after conceding 5 its specific identity with the 

 earlier-published Lithophyllum crispatum Hauck. The typical 

 form of Foslie's Lithothamnium philippii is said by him 6 " to have 

 its hypothallium distinctly marked and vigorously developed, form- 

 ing a coaxilate layer," but the "coaxial" character is essentially 

 denied by Mme. Lemoine 7 to what she considers the same species 

 under the name Lithothamnium crispatum Hauck. The perithallic 

 cells of the crustaceous parts of Lithothamnium isthmi appear to 

 average considerably smaller than those of L. crispatum (L. phi- 

 lippii) according to the measurements given by Lemoine and by 

 Foslie. The tetrasporangial conceptacles of the Lithophyllum de- 

 cussatum of Hauck {Lithothamnium philippii Foslie) are stated by 

 Hauck to be "SOOjjl bis 1 mm." in diameter, while in Lithothamniwnt, 

 isthmi they are only 240-550 y. in maximum width. Moreover, 

 unless we are mistaken in connecting the fruticulose parts of the 

 Panamanian fossil with the crusts, Lithothamnium isthmi develops 

 numerous solid anastomosing branches, while in L. crispatum the 

 short branchlike excrescences are mostly hollow, infundibuliform, 

 or scjrphiform. These fruticulose conditions, which comprise a 

 large part of the material collected by MacDonald and Vaughan, 

 suggest in external form certain states of the living West Indian 

 Lithophyllum daedaleum Foslie and Howe, which also presents 

 itself in both crustaceous and fruticulose conditions. Occasionally 

 an unusually long subterete branch may resemble in form a frag- 



iMem. Soc. Imp. Sci. Nat. Cherbourg, vol. 12, pi. 6, fig. 14, 1866. 



2 Ann. Inst. Oceanog., vol. 2, pt. 2, fig. 60, 1911. It is of interest to note that Mme. 

 Lemoine, basing her system of classification primarily upon the vegetative structure of 

 the thallus, leaves Lithothamnium lichenoides in the genus Lithophyllum, notwithstand- 

 ing the fact that its tetrasporangia are borne as in the genus Lithothamnium of modern 

 writers. In the same way she would doubtless place Lithothamnium isthmi in the genus 

 Lithophyllum, even though this species (or its type at least) clearly has the tetrasporan- 

 gial conceptacles of the conventional Lithothamnium. 



3 Hauck, F. Die Meeresalgen Deutschlands und Oesterreichs, pi. 1, fig - . 7. See also- 

 pl. 1, fig. 1, of Foslie's Die Lithothamnien des Adriatischen Meeres und Marokkos (Wiss. 

 Meeresuntersuch, Helgoland, vol. 7, pt. 1, 1904). 



* Foslie, M. On some Lithothamnia. Kgl. Norske Vidensk. Selsk. Skr., 1897, pt. 1„. 

 p. 7, 1897. 



5 Wiss. Meeresuntersuch, Helgoland, vol. 7, pt. 1, pp. 13, 14, 1904. 

 Kgl. Norske Vidensk. Selsk. Skr., 1900, pt. 1, p. 5, 1900. 

 7 Ann. Inst. Oceanog., vol. 2, pt. 2, p. 80, flg. 38, 1911. 



