KOFOID AND SWEZY: UNARMORED DINOPLAGELLATA 261 



DiAGXOSis. — A medium sizerl species with dorsoventrally compressed, dis- 

 coidal })ody, its length 1.1 transdiameters ; girdle without displacement; sulcus 

 short. Length, 60/^. Fresh-water ponds near ^laudach, Germany, through the 

 winter mouths. 



Description. — A mediiun sized species with ilisklike body, flattened dorsoventrally to a thin 

 plate, its length 1.1 transdiameters. The hypocone exceeds tlie epicone in length by about 0.2 of 

 its own length. In ventral view the epicone is snbhemis])lierieal with the right side of the semi- 

 circle longer tlian the left. Its lengtli is about 0.4 of the total Icngtli of the body in the midventral 

 region. The girdle curves posteriorly on the dorsal side, turning anteriorly before reaching the 

 midventral region, giving the right side of the epieone at the edge of the disk a length of 0.5 the 

 total length of the body. The hypocone is asymmetrical with a blunt antapex, longer upon the 

 right side. 



The girdle, as well as the sulcus, is incomplete in Lauterborn's (1898) figures. Its distance 

 from the apex in the midventral region is about 0.4 of the total length of the body. It makes a 

 posterior sweep on the dorsal side of the body, turning anteriorly in the last quarter of its course 

 to the neighborhood of its origin. The furrow is rather deeply impressed, about 0.07 trans- 

 diameter in width, with sharply marked borders. The sulcus is only faintly indicated by a 

 short line on the hypocone. The transverse and longitudinal flagella apparently take origin at 

 points not far distant from the junction of the girdle and sulcus. 



The nucleus is ellipsoidal and located in the central region of the body. It is filled with 

 coarse chromatin granules. Its major and minor axes are 0.3 and 0.2 transdiameters in length 

 respectively. The cytoplasm is filled with spherules of various sizes, and rounded, yellow-brown 

 chromatophores. 



DiMEXsioxs. — Length, 661^ ; transdiameter, 60/^ ; axes of nucleus, 19^ and 14/^. 



Occurrence. — This was figured by Lauterborn (1894, 1899) from fresh- 

 water ponds near Maudach and Ludswigshafen, Germany, through the winter 

 months. 



Comparisons. — This species is tentatively allocated in the subgenus PacJti/- 

 dinmm because of its differentiated peripheral cytoplasm, marked by radial 

 structures. Lauterborn (1898) explicitly notes a clearly marked alveolar layer, 

 but does not give its location. There is no other species in the genus approaching 

 G. tenuissimum. The describer calls attention to its similarity to Glenodinium 

 foJiaceuw, a flattened thecate species of the Peridinioidea. 



Gymnodinium tintinnicola Lohmann 



Text figure BB, 1.3 

 Gymnodinium tiidiiDvicola Lohmann (1908), pp. 259-260, 266, 366, pi. 17, fig. 6a-c. 



The probability that some of the minute Gi/nnwdi)iiiiiii found in the plankton 

 are swarm spores of parasitic species belonging, it may be, to other genera has 

 been demonstrated by Lohmann 's discovery of a minute species which he has 

 named G. fintinnicoht. He found this organism emerging as a parasite from 

 Ti)itinnopsis nudchi, one of the lorica-forming ciliates of the marine plankton. 

 There were about ten of these "sjiores" in the ciliate. They have, in the free 

 state, the t\']jical form of Gijiini<j<liiiiH))i with the two characteristic flagella, the 



