312 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



phorus; sum-total, thirteen species. A new Scellus from British Colum. 

 bia is also described here. 



It is rather remarkable that two species of Hygroceleuthus should 

 have been brought from the lower altitudes of California, together with 

 only one species of Dolichopus, while only four other species of Hygroce- 

 leuthus* are known from the whole world, against more than a hun- 

 dred Dolichopus. It is also remarkable that among the few Dolichopus 

 from California described by Mr. Thomson, one should also be a Hygro- 

 celeuthus, perhaps identical with one of mine, but too insufficiently de- 

 scribed, in a female specimen, for identification. 



One of the Tachytreclms is apparently identical with a species from 

 the Eastern States; the other one is closely allied to, bat certainly dif- 

 ferent from, another species from the same region. 



The most remarkable discovery in this family is the new genus Poly- 

 medon, with its extraordinary development of the face and of the cilia of 

 the tegular. 



It would seem that, on the whole, Dolichopodidce are but poorly rep- 

 resented in California. The places to look for them, in the vicinity of 

 San Francisco, are probably the marshes surrounding the bay, a local- 

 ity which I have neglected to visit. In the Sierra, they are somewhat 

 more abundant, in species as well as in specimens. 



All the necessary information about the Dolichopodidw, including the 

 definition of the genera, will be found in Dr. Loew's work on them, in 

 the Monographs of N. A. Diptera, vol. ii. 



Hygroceleuthus. 



I refer to this genus two species, in which the face descends as far 

 as the lower corner of the eye ; moreover, the two basal joints of the an- 

 tenna^ especially in one of these species, are considerably enlarged, a 

 character which belongs to the typical Hygroceleuthus (compare Loew, 

 Monographs, etc., ii, 17). 



1. Hygroceleuthus crenatus n. sp.—Male.— First antennal joint 

 longer than usual, expanded on the inside so as to meet a corresponding 

 expansion of the other antenna; second joint nearly as long as the first, 

 on the inside of its basal half a similar expansion ; both joints are black, 

 except these enlargements ou the inside, which are reddish-yellow ; the 

 first joint is beset on the outer and upper side with long and dense black j 

 pile ; the second has some hairs on its end ; third joint comparatively 

 small, subtriangular, Mack; the dorsal arista appears unusually stout, 

 from the dense pubescence which covers it. Face yellowish-white; ci- 

 lia of the inferior orbit rather stout, golden-yellow. Thorax and abdo- 

 men bright metallic-green; tegular yellow, with yellow cilia, sometimes 

 mixed with black hairs ; lamellae of the hypopygium yellow, with a nar- 

 row black border. Legs yellow, including the fore coxae, which have a 



* Two iu Europe, one in Siberia, one in North America (Loew, Monogr., ii, 17). 



