26 Descriptions of New 



(very abrupt in most, but less so in some specimens,) before 

 reaching it, the third after having been interrupted near its 

 base by the subhumeral cavity, runs on but does not reach as 

 far as the former, the 4th does not leave the region of the 

 shoulder, the last on either side is very prominent at the base 

 but soon forms an abrupt declivity and runs on as a low ridge 

 to below the middle. The back of all these costse is obtusely 

 dentated. The interstices are marked with large, shallow, 

 transverse impressions. The head of the insect is rather large 

 and even. The mandibles are furnished with an obtuse sub- 

 apical tooth, the 2 lower thirds are ciliated. The maxilla; 

 have the apex of the outer lobe externally enlarged, rounded 

 off and furnished with 3 strong teeth replaced by cilia on the 

 inside, the inner lobe is conic and similarly provided with teeth 

 and cilia, however, much thinner and finer. The maxill. palpi 

 are robust, the last joint is inflated at the base. The antennal 

 club is hairy, dark (whilst the remaining joints are yellowish), 

 conic and somewhat securiform, the 6th joint being inserted 

 on one side of the 7th. The legs are robust, the tibiae slightly 

 curved, obliquely truncated at the end, furnished with spines 

 along the outside and with distant cilia along the inner. 



21. Hydrochus lacustris. N. 



H. elongatus,. subdepressus, supra metallicus, iridescens, subtus piceus 

 pedibus, antennis, palpis elytrorumque margine magis minusve brunneis, 

 niento cyaneo. Long. corp. 1-1^ lin. 



Palpi maxill. robusti art. ultimo elliptic© leviter inflato. Mandibular 

 apice bifidse. Antennarum clava dense pilosa. Thorax oblonge quadratus 

 basin versus angustatus,basi medio productus, cum capite profunde puncta- 

 ta. Elytra ad humeros oblique truncata, apicem versus sat fortiter an- 

 gustata, profunde striato punctata. Tibia? extus spinulosse. 



Specimina nonnulla in lacu Colomb. legi. 



The head is robust, broader than the thorax, the eyes large 

 and prominent. The femora, the last joint of the maxill. palpi, 

 the mandibles, and the tarsal joints are dark towards the apex. 



