94 University of California Publications in Zoology [Vol. 13 



ondary, tertiary, and quaternary spines appear exactly equal in size, 

 with the primary always, however, somewhat larger. Here again we 

 note the enlargement of the posterior end of the body to accommodate 

 the added number of spines. In all other respects this forma is identi- 

 cal with D. e. forma ccaudatum. The body dimensions are given on 

 page 95. 



6. Diplodinium ecaudatum forma cattanei Fiorentini 



Diplodinkim Cattanei Fiorentini (1889), pp. 16-17, pi. 3, figs. 4, 5. 

 PI. 5, fig. 10 



This form is not very abundant. Not only is its presence in cattle 

 the exception, but even when present it occurs only in small numbers. 

 The distinguishing feature of this form is the possession of five pos- 

 terior spines. The quintary spine {sp. 5) occurs on the right side just 

 dorsal to the primary spine and curves dorsally and inward. In 

 every case of D. e. forma cattanei examined the arrangement of 

 spines was as shown in the figure (pi. 5, fig. 10), i.e., a very large 

 ventral spine {sp. i), a large secondary spine {sp. 2) normally placed, 

 a very much smaller tertiary spine {sp. 3) also normally located, a 

 very broad, somewhat flattened quaternary spine {sp. 4) on the left 

 side, and a second very small quintary spine {sp. 5) on the right side. 

 In every case the two spines of the right side were so small and the 

 two spines of the left side so large that it was necessary to view the 

 spines from the right side in order to see and draw the small spines. 

 In all other respects the morphology of the spines and of the body 

 was what w^ould be expected. The dimensions of this form are given 

 below. 



Considerable hesitation was at first experienced in assigning Diplo- 

 dinium cattanei, as described and pictured by Fiorentini (1889), to 

 the Diplodinium ecaudatum series. As a matter of fact, it was not at 

 all certain that the five-spined form described by this investigator was 

 identical with the one occuring in my material. But with the dis- 

 covery of all the intermediate forms of the series, viz. : the two, the 

 three, and the four-spined forms, coupled with the fact, on the one 

 hand, that the five-spined form which was present in my material 

 was so surely a member of the ecaudatum series, and on the other 

 hand, that with the exception of the number of vacuoles pictured for 

 D. cattanei by Fiorentini (1889, plate 3, fig. 5), my five-spined form 

 corresponded very closely to his, it became evident that the two were 



