Diaiomacem from the Caspian Sea. By A. Grunow. 687 



M. Borreri are in groups and irregularly disposed, so that tlie 

 valves have a shagreen-like appearance. 



Podostra Isevis Greg, does not appear to me to differ from 

 P. Moniagnei. 



P. hormoides (Montague nee W. Smith) = P. nummuloides 

 Ehr. — According to the original examples, approaches very near to 

 P Montagnei, and differs principally in the valves being less con- 

 vex. The structure is very similar, but the puncta are more 

 distant (18 in -01 mm. against 21-22 in P. Montagnei), and 

 the larger puncta are fewer in number and more radiant. 



[The arrangement adopted by Herr Grunow is that of Pfitzer, 

 who divides the Diatomaceae into two groups, Placochromaticae and 

 Coccochromaticas. See 0. Meara's Analysis of Dr. Pfitzer's System 

 in 'Q. M. J.,' vol. xii., n. s., and M. P. Petit's in 'M. M. J.,' vol. 

 xviii.— F. K.] 



[Since the preceding paper was written I have received from 

 my friend Herr Grunow the following notes on Coscinodiscus, Hyalo- 

 discus, and Podosira. — F. K.] 



Coscinodiscus nohilis Grun. — This is the form I refer to 

 C. regius Wallich in my paper on Diatoms from the Caspian Sea 

 (p. 27* : " Zu dieser durch ein glattes Centrum ausgezeichneten 

 Gruppe gehoren noch C. perforatus Ehr. und C. ajyiculatus Ehr., 

 so wie C. regius Wallich "). It is not C. regius, of which, through 

 the kindness of Mr. Kitton, I have since seen specimens. It is 

 much larger (1-4 mm.) than C. nohilis whose greatest diameter is 

 •54 mm. C. regius has no smooth centre, but a wide space in 

 the middle covered with irregularly disposed puncta, and distant, 

 variously shaped, slightly curved spines. The valves are cylindrical 

 and in s. v. have radiant lines of puncta (3 in "01 mm.). On the 

 cylindrical part (f. v.) the puncta are parallel (5 in * 01 mm.) and 

 are separated from the radiant rows by a circular smooth space on 

 the upper edge of the valve. The slightly convex valves of C. 

 nohilis have a smooth centre and closer and smaller puncta (about 

 7 in '01 mm.) which become hexagonal as they approach the 

 margin, and are separated into groups by radiating lines which are 

 sometimes scarcely visible. I have a smaller form from the Samoa 

 Islands (*06-'13 mm.) with a smooth centre and more radiating 

 puncta (5 in '01 mm.). It resembles C. ajnculatus Ehr., and 

 might be named C. apiculatus var. Samoensis. A similar form 

 occurs in tlie Monterey deposit. C. nohilis was collected by 

 Krock, and communicated to me by Professor Cleve. PI. XXI., 



Fig. 1, :*-p. 



* Not noticed in my vesune. — 'E. K. 



2 z 2 



