322 M. C. Mereschkowsky on the Hydroida. (Edionychis Chevrolatii. (E. late ovata, convexa, nitida ; subtus, cum capite (encarpis flavis exceptis), nigra, abdomine piceo, margine externo segmentorumque marginibus pallidioribus ; supra j&ava ; thorace Isevi, impunetato ; scutello trigonato, nigro ; elytris sat remote, tenuiter punctatis, utrinque vitta suturali, altera submarginali, his apiee conjunctis, tertiaque discoidali, paullo ante apicem abbreviata, nigro-cyaneis ; limbo exteriore angusto piceo. Long. 3 lin. Hah. Mexico. Vertex smooth, impunctate j inner orbit of eye and the upper surface of the front impressed with large, round punc-tures ; lower portion of front very finely strigate ; encarpae separated from the front by a distinct transverse groove, sub-quadrangular, pale fulvous ; carina strongly elevated ; second and third joints of antennas 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. Elytra 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.] XXXVI. — Studies on the Hydroida. By C. Mereschkowsky. [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
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