322 M. C. Mereschkowsky on the Hydroida. 
Gidionychis Chevrolatit. 
G. late ovata, convexa, nitida; subtus, cum capite (encarpis flavis 
exceptis), nigra, abdomine piceo, margine externo segmentorumque 
marginibus pallidioribus ; supra flava; thorace levi, impunctato ; 
scutello trigonato, nigro; elytris sat remote, tenuiter punctatis, 
utrinque vitta suturali, altera submarginali, his apice conjunctis, 
tertiaque discoidali, paullo ante apicem abbreviata, nigro-cyaneis ; 
limbo exteriore angusto piceo. 
Long. 3 lin. 
Hab. Mexico. 
Vertex smooth, impunctate; inner orbit of eye and the 
upper surface of the front impressed with large, round punc- 
tures; lower portion of front very finely strigate ; encarpz 
separated from the front by a distinct transverse groove, sub- 
quadrangular, pale fulvous; carina strongly elevated ; second 
and third joints of antennz nearly equal in length. Thorax 
three times as broad as long; sides nearly straight, very 
slightly converging behind the middle, thence converging and 
slightly rounded to the apex; anterior angles mucronate ; 
basal margin bisinuate on either side, the median portion not 
produced, obtusely truncate ; upper surface shining, impunc- 
tate; lateral margin broadly reflexed. Scutellum trigonate, 
its apex acute. LElytra broader than the thorax, increasing 
in breadth from the base towards the apex, the latter broadly 
rounded ; above moderately convex, longitudinally excavated 
along the base of the suture, the depressed surface rather 
strongly and coarsely punctured. 
[To be continued. | 
XXX VI.—Studies on the Hydrotda. 
By C. MrerescHkowsky. 
[Continued from p. 256. } 
III. Systematic Facts. 
As I am now busy preparing a complete description of all 
the Hydroids occurring in the Russian seas, which will 
shortly appear in my native language, I shall here give simply 
a list of the species which I have met with in my two visits. 
to the White Sea, and only describe a few of the new species 
and the new genera. The deficiency of material in respect of 
Hydroids in our zoological museums sometimes renders the 
determination of the species very difficult, and in some cases 
rather doubtful ; for frequently it is very desirable to compare 
two specimens, one of which is already determined. But 1 
