FROM THE ISLAND OF SOCOTRA. 515 
firmly coherent, often forming filaments of considerable length ; 
valves narrow-linear, suddenly narrowing near the rounded 
apices; margins punctate; the strim. become delicate as they 
approach the centre. Length of valve :0090—01606, breadth 
'0003.—Cyprus; Belgaum (India); island of Socotra. 
The remaining forms observed are such as are usually met 
with in freshwater gatherings. It will be seen that, with the 
exception of two or three species of Navicula, they are all 
parasitic :— 
Cocconema lanceolatum. | Cocconeis pediculus. 
cymbiforme. | Cyclotella Meneghiniana, var. 
——— Cistula. | Eunotia pectinalis. 
Cymbella bengalensis. | Navicula spherophora. 
Gomphonema intricatum, var. ovalis. 
affine. Amphora ovalis. 
acuminatum. | Mastogloea Dansei. 
Turris. | elliptica. 
——— constrictum, var. subcapi- ^| Epithemia gibberula. 
tutum. |! Achnanthes linearis. 
The Diatomacez above recorded do not afford any indication 
of connexion with India or Africa, either by bird- or water- 
carriage or former continuity of land. Diatomaceous gatherings 
from localities wide apart are sometimes difficult to distinguish 
from each other. This is not unfrequently the case with fossil 
deposits, partieularly those of freshwater origin. 
DESCRIPTION OF PLATE XLVIII. 
Fig. 1. Cerataulus socotrensis, Kitton, n. sp. X 600 diam. 
2. Frustule of C. socotrensis. x 200. 
3. Cerafaulus levis (Ehrenb.). x 400. 
4. Fragilaria Ungeriana, Grun.  Frustules, x 350. 
5. Ditto. Part of valve, x 600. 
6. Cymbella bengalensis, Grun. X 700. 
