ANNULOSA JAVANICA. 29 



Caput ut in genere Taro Clairv. Thorax subquadratus canaliculars postice angustior angulis anticis 

 rotundatis. Corpus valde depressum. 



Obs. This genus is intermediate between Tarus Clairv. (Cymindis Lat.) and Helluo, Bon.; 

 from the latter it differs in the labruni not being acuminate, and from the former in the shape of 

 the maxillary palpi and thorax. 



36. Bimaculatus. P. ater labro palpis antennis pedibus elytrorumque macula media ferrugineis elytris sulcato- 

 striatis. 



Long. corp. \ 

 Caput atronitidum transverse punctatum facie laevi bipunctata antice truncata. Thorax atronitidus punc- 

 tatus. Elytra atra depressiuscula sulcata, sulcis profunde striatis macula versus basin ovali ferru- 

 ginea. Corpus subtus atrum. 



Obs. This species may perhaps be found too near the Carabus Stigma of Fabricius, but cer- 

 tainly is not the same with the Helluo distactus of Escholtz, described as a Javanese insect in 

 Wiedemann's Zoological Magazine ; although I suspect the latter to be also a Planetes, from 

 what Dr. Escholtz says of the thorax being proportionally longer than in his Helluo impictns, a 

 species found in Bengal. Helluo distactus, differs from Planetes bimaculatus in being striated and 

 having each stria marked with two rows of points. None of these species, however, are true 

 Helluones, and the mistake has arisen from the continental entomologists being so little ac- 

 quainted with the original Helluo of Bonelli, Helluo costatus, which is a New Holland insect. 



Stirps. 2. HYDRADEPHAGA. Hybrocanthabi Lat. 



In the Geodephaga the binary subdivision of the groupe is not very distinct, because the cha- 

 racteristic marks of each subdivision insensibly pass into each other. In this stirps of aquatic 

 carnivorous insects it is however different, for the binary subdivision is remarkably distinct, 

 and I know as yet of no insect which can satisfactorily fill up the hiatus that occurs between 

 the Gyrini of Linnaeus and his Dytisci. 



The larva? of the Hydradepluiga differ from those of Geodephaga in being truly aquatic, and 

 therefore breathing by tracheal branchiae. Their prothorax also, or that segment of the body 

 which corresponds with what is usually called the thorax of the perfect insect, is not of a 

 more corneous texture than the other segments. 



I shall not at present attempt to divide the Hydradephaga into families, but content myself 

 with giving the following approximation to a natural arrangement. The genus Hoplitus of 

 Clairville seems to form the type of a family which I have not here ventured to designate. 



Hydradephaga. Families. 



1 . Normal groupe, r 



Pedes antici longi, J — ] ■ Gynmia. 



Antennas breves. j 



Gyhinds Lin. (_ 



2. Aberrant groupe. , 3. * * * 



Pedes antici breves, | 



Antennae setaceaa lineares. \ 4. Di/tiscidtn. 



Dytiscus Lin. ( c * # # 



Fam. 



