116 GEO. H. HORN, M. D. 



are not easy to define. The posterior coxae being separated a relationsliip 

 seems to be indicated with the Promecognathini and Cychrini, especially 

 with the latter by the more widely inflexed sides of the elytra but it 

 differs widely from either by the structure of the anterior tibias. The 

 presence of a setigerous puncture on the mandible is a very curious 

 addition to the other characters, as I observe that this is in nearly if not 

 quite all other cases associated with riparial habits which cannot from 

 my observation be said of Metrius. 



Chaudoir (Bull. Mosc. 1861, i, p. 510), places the present genus in 

 his tribe Migadopidae, and while but one other genus of that tribe is 

 known to me I feel very safe in saying that the present can not be 

 allowed to take place with it. In the synoptic table the structure 

 of the metasternal side pieces is used for the separation of Migadops 

 ( Brachycaelus) from Metrhis. In the specimen of Mig. virescens before 

 me the met-epimera are not distinct while in Metrius the suture is 

 sometimes visible and in others not. 



Tribe XII.— Mystropomini. 



Antennse arising under a slight frontal jilate, four basal joints glabrous. Eyes 

 small, round, not prominent, distant from the mouth beneath. Head oval, with 

 two small supra-orbital setse. Clypeus rather large with two small setigerous 

 punctures each side. Labrum short, sinuate in front and plurisetose. Mandibles 

 acute at tip, feebly arcuate, toothed at middle, no setigerous puncture externally. 

 Maxillae arcuate and acute at tip, spinulose and ciliate internally, outer lobe 

 biarticulate, palpi rather stout, the terminal joint longer, flattened, broader ex- 

 ternally with the tip rounded. Mentum large, deeply emarginate and with a 

 large median emarginate tooth, ligula cuneiform suddenly broader in front, the 

 tip slightly prolonged in front and sexsetose. paraglossse rather broad, adherent 

 in their entire length and obtuse at tip, the palpi stout, terminal joint as in 

 the maxillary. Thorax without marginal setse. Elytra not margined at base, 

 (scutellum indistinct), sides rather widely inflexed, margin entire not interrupted." 

 Presternum obtuse at tip, not prolonged, anterior coxal cavities closed behind. 

 Mesosternum narrowly separating the coxse, the epimera indistinctly separated 

 from the episterna but distinctly reaching the middle coxal cavities. Metasternal 

 episterna short and broad, the epimera distinct, posterior coxse separated. Legs 

 moderate in length. Anterior tibise deeply obliquely grooved within the spurs 

 both terminal. Middle tibise ciliate with_ short depressed hairs externally and 

 within, the outer edge of posterior tibise not ciliate, the tibial spurs rather short. 

 Tarsi slender, the first joint as long as the two following. 



The tarsi are said by Chaudoir to be similar in the sexes. 



For a specimen of Mystropomus subcostatus Chd., the only known 

 member of the present tribe, I am indebted to Mr. H. W. Bates. 



Of all the genera which I have studied this has caused me the greatest 

 surprise from the position in which it is placed and which appears to be 

 now accepted without (juestion. 



