166 Illinois State Lahoratory of Natural History. 



*' Found in the Sierra Nevada Mountains, California, at a 

 height of from 8,000-10,000 feet above sea-level by G. 

 Eisen. Appears to be very common in small pools in this 

 locality. 



"This Diapto7nus is very distinct from all known species 

 on account of the peculiar form of the first abdominal seg- 

 ment. In this respect it approaches D. rouhaui Eichard, and 

 the genus Epischura Forbes. In the case of these Copepoda, 

 however, it is the male which is distinguished by the irregu- 

 larity of the abdomen. The name which I have given it 

 refers particularly to the shape of the female abdomen."* 



There is nothing to add to the above description of this 

 species except that the furca are delicately hairy within, a fact 

 neither shown in the drawings nor mentioned in the original 

 description. The last thoracic segment of the female is 

 strongly produced, and the first abdominal segment greatly 

 dilated at its anterior part. The process on the first abdomi- 

 nal segment is even larger in some cases than represented in 

 the original drawings. 



In the male also the last thoracic segment is produced, but 

 not so much as in the other sex. The fifth pair of legs are 

 very similar to those of D. siciloides, from which they may be 

 distinguished by the shape of the right inner ramus and of 

 the hyaline lamina on the first segment of the outer ramus of 

 the right fifth leg. Both inner rami are delicately hairy, but 

 I fail to find the smooth, cushion-like process on the outer 

 margin and at the base of the left inner ramus which is fig- 

 ured in the original drawings but of which no mention is 

 made in the text. 



The females of D. sif/nicauda and /). tryhomi both have a 

 "dorsal process," and in this respect approach D. sanguineus 

 Forbes. 



Individuals of this species were kindly sent me by Dr. 

 Lilljeborg, but were unavoidably delayed until after this 

 description was completed. There was no time to rewrite it, 

 hence these remarks are in the form of addenda. The same 

 is true of tryhomi, eiseni, and francisca7ius. 



*Lilljeborg's description and remarks from de Guerne et Kichard, 'b'Jb. 



