600 RITTER. 



secondary processes on the primary ones. In young individuals 

 the processes are simple ; in older ones, however, there are a 

 few short secondary processes on the primary ones. 



The author describes the branchial sac as having seven folds 

 on each side ; as a matter of fact there are eight, but in a young 

 specimen it would be very easy indeed to fail to recognize all of 

 them. The detailed structure of the branchial sac I have 

 thought best to give complete, partly because of the inadequacy 

 of von Drasche's description, and partly because of its very pe- 

 culiar structure (PI. XIX., Fig. 25). There are, as already 

 said, eight folds on each side. These are large and closely 

 placed. Each has about twenty internal longitudinal bars, and 

 the interspaces between them two or three bars. The stigmata 

 are elongated transversely to the direction of the endostyle and 

 the folds of the sac. They are somewhat irregular in shape, size 

 and arrangement, but on the whole they are arranged in series 

 and in such fashion that a space is left between two adjacent 

 series, against which the ends of the stigmata of each series abut. 

 These spaces — longitudinal vessels they might be called — usually 

 alternate with the internal longitudinal bars (Fig. 25, 1. v.^ 

 and 1. v."). 



The internal transverse vessels, or bars, are small and numer- 

 ous, the typical arrangement being one between each two stig- 

 mata. Fig. 25 t. v.^ These small transverse vessels connect 

 with the internal longitudinal bars. Some of them cross the in- 

 terserial spaces, or longitudinal vessels, and some do not, but 

 terminate in these spaces. In addition to the small internal trans- 

 verse vessels there are also larger ones. Fig. 25, t. v.\ there 

 being about ten of the smaller to one of the larger. The result 

 of this arrangement is that typically each mesh of the branchial 

 sac contains a single stigma. 



von Drasche desribes and figures the stigmata to be nearly 

 round. So far as there is any elongation, however, this is in the 

 transverse direction, as shown by his PI. XX. Fig. 9, I have 

 for some years believed the C. castancifonnis of von Drasche to 

 be identical with C. villosa Stimpson, '64. Veiy recently, how- 

 ever, Herdman, '98, has re-described what he believes to be C. 



