462 ORDER CILIO-FLAGELLATA. 



the dorsal angle with a tooth-like process; surface of cuirass apparently 

 smooth in the living state, exhibiting delicate transverse striae when 

 isolated by maceration ; colour bright yellow. Length 1-430". 

 HAB. Salt water. 



According to Ehrenberg this species is highly phosphorescent. Claparede and 

 Lachmann have however failed to confirm the observations of the German authority. 



Prorocentrum lima, Ehr. 



Cuirass ovate, inflated and rounded posteriorly, becoming gradually 

 narrower towards the anterior region ; the anterior border slightly emarginate ; 

 surface sparsely asperate. Diameter 1-1152" to 1-864". 



HAB. Salt water, Adriatic. Colour yellowish-brown. 



Doubtful Species. 



The minute Prorocentrum viridis of Ehrenberg, reported to be of ovate or sub- 

 orbicular form with a rounded posterior and shortly pointed anterior extremity, 

 enclosing green granules, length i-noo", inhabiting the Baltic, is insufficiently 

 characterized for identification as a representative of this genus. 



GENUS X. DIMASTIGOAULAX, Diesing. 



Animalcules free-swimming, encuirassed, traversed by an equatorial 

 ciliated furrow ; flagella two in number, issuing from the same point of 

 origin in the equatorial groove; cuirass extended into horn-like pro- 

 longations. 



Excepting for the presence of the two flagella, the as yet single known represen- 

 tative of this genus corresponds in form and structure with those of Ceratium. 



Dimastigoaulax cornutum, Ehr. sp. PL. XXV. FIGS. 51 AND 52. 



Cuirass compressed, quadrilateral, the dorsal surface convex, the ventral 

 one concave ; the anterior segment bearing two nearly straight horn-like 

 processes, and the posterior a single short median one, neither of them 

 exceeding one-half of the diameter of the body ; flagella subequal, 

 equalling or surpassing the body in length. Length 1-280" to 1-140". 



HAB. Fresh water; colour brown or slightly green. 



This species, which is synonymous with the Peridinium cornutum of Ehrenberg, 

 Ceratium hirudinella of Dujardin, and Ceratium cornutum of Claparede and Lachmann, 

 has been selected by Diesing * as the type of the present genus on the strength of the 

 evidence concerning its possession of two flagella, yielded through the investigations 

 of Lieberkuhn and Claparede and Lachmann. It must be at the same time noted 

 that this evidence is by no means conclusive; the last-named authorities, while 

 figuring two flagella in the drawing, as here reproduced, were by no means certain 

 as to their existence, and did not feel justified, under such circumstances, in 

 connecting the species with a new generic title. The Peridinium Carolinianum, 

 found by Mr. J. W. Bailey at Grahamsville, South Carolina, and described under 

 the foregoing title in the ' Smithsonian Contributions to Knowledge ' for December 

 1850, is apparently identical with this type. 



'Revision der Prothelminthen," ' Sitz. der Kaiser. Akad. der Wiss. Wien,' 1865. 



