F. KITTON ON SOME NEW DIATOMACE^E. 23 



These forms occurred in a gathering from Marble Head, Mass., 



U.S. 



DESCRIPTION OF PLATE IV. 



Fig. 1. — Aulacodiscus Sturtii. X 600 dia. 

 2. — Podosira maxima, X 400 dia. 

 3. — ,, diagrammatic section of valve. 

 4. — A mp Ja pleura pettucida, X 400 dia. 

 4a. — „ apex, x 800 dia. 



5. — Surirella crinata, X 400 dia. 



a-h, ideal sections of do. 

 6. — Sceptroneis clavv.s, X 360 dia.* 



a, superior apex of do., X GOO dia. 

 7. — Naticula Lyra, abnormal, X 600 dia. 



This valve is apparently slightly abuormal, the pseudo raphe is not central, 

 and one angle of the broad apex is lower than the other. Fig. a represents a 

 fragment of another valve. 



* Shows the moniliform character of the striae. 



