KONGL. SV. VET. AKADEMIENS HANDLINGAK. BAND. 18. N:0 5. 19 



RutilJiria Grev. 



1. Rutilaria recens Cl. N. Sp. 



Valve plane, elliptic or elonfjate with acute ends. It is covered with nuinerous 

 scattered puncta, which sometimes are arranged in irregular lines. Besides these there 

 are in the centre of the valve some more strongly marked puncta, and which seem to 

 belong to another stratum of the valve. The margin has a row of puncta, which are, 

 as may be seen in the F. V., short spines. In the F. V. the ends of the valve termi- 

 nate in short processes. 



Length 0,0370,11 mm. Breadth 0,02 mm. 



PI. IV, fig. 57, a. """/j (an abnorm specimen having no puncta on a part of the 

 valve), b. ^/\ small specimen. 



Gallapagos Islands (Eugenie Exp.). 



The genus Rutilaria established by Dr- Greville, comprises only some few spe- 

 cies, all fossil. These are R. Epsilon Grev., rare in Monterey stone, R. superba (and 

 var.? ventricosa) Grev. and R. elUptica Grev. from Barbados. They all have the cu- 

 rious markings in the centre of the valve, which are elevations above the level of the 

 frustule, as is visible on the fig. 10, PI. XI, T. Micr. Soc. Vol. XIV. In our recent 

 species these markings are represented only by the strongly marked puncta. From 

 Geeville's fig. of the F. V. of R. ellijjtica and R. superba it is evident that the valve 

 is plane and that its apices are produced into processes, and farther that tlie margins 

 of the frustule are bounded with a row af setas, exactly as in our species. 



The position of Rutilaria is somewhat uncertain. Greville has pointed out its 

 relationship to Nitzschia and Fragilariea\ Prof. Hamilton Smith places it among the 

 Melosiraj. It has however no real affinity with Nitzschia or Melosirai, but is very 

 nearly allied to the genus Cyiiiatosira Grun., of which the only known species C. Lo- 

 renziana Grun. has also marginal bristles. The Cymatosira is without doubt nearly 

 related to Dimerogramma. 



Mr. KiTTON writes to me in a letter about a new species of Rutilaria from the 

 Californian deposits, Rut. obesum Grev. Mpt. The valve has 3 inflations, the central 

 being the largest; the apices are shortly cuneate; one third of the area is smooth, the 

 remainder distinctly covered with irregular markings. The central nodule consists of 

 a nebulous circular spot, u[)on which is placed a short spiral (?) ring. Margin distinctly 

 punctate. Mr. Kitton has seen about half a dozen specimens of this species, all 

 frustles, and in no case was he able to separate the valves. I crushing partially one 

 specimen in balsam, he observed that the nebulous central nodule was the base of a 

 siliceous isthmus, connecting the two valves. 



