453 



GRAYA. 



Ploiaria petasiformis Pant. (Batill. Mag., I., 1886 ; p. 48, pi. 



29, f. 295, sub Hemiaiilo ; II., 1889, p. 83, pi. 28, f. 403, 405), represented in the 

 text (fig. 186). Dr. Pantocesk has found this form in the deposits of Hungary. 

 The valve is about 5 to 6 c.d.m. in length, and about 2-5 c.d.m. in breadth. 



GENUS 123 GRAYA BRUN & GROVE, 1892. 



Fig. 187. 

 Graya Argonauta. 



a. Girdle view. b. Valve view. 



Valve broadly elliptic, with margin much elevated near the median 

 portion. Centre umbilicate, often surrounded with a small area 

 sometimes linear narrow, at other times subrhomboidal. Striae delicate, 

 finely punctate, radiating round the umbilicus. Girdle face very broad, 

 appearing to be undulate in consequence of the margin of the valve 

 being elevated ; connecting membrane very delicately punctate, 

 Frustules united into very short filaments. A single species : 



Graya Argonauta Br. and Gr. (fig. 187), after Professor 



Brun's specimen. This form, which has only been found and named since 

 1892, appears to have escaped the observation of diatomists, since it is not 

 excessively rare. It has been found in the fossil deposits of Maryland 

 (Brun !), Sta. Monica (Thum. !), and Oamaru (Weissflog). In the specimens 

 from Maryland the median area is elongated ; in those I have from Sta. 

 Monica, it is rhomboidal, and lastly, it is absolutely wanting in my specimen 

 from Oamaru. 



