27 



iind s()iciers, is conipk-lely lillcd iiUo llie nioulli. The cavily of the inoutli is 

 accordingly dorsally and laterally encompassed by Ihe lahruni; in this and just 

 behind it we find several systems of muscles, the courses of which are indicated in 

 the figure, but the detailed activities of which ought probably to be regarded as 

 almost impossible to unravel in the minute Danish species of this order." 



To this long quotation I will only add a few suggestions. There seems not 

 to be so sharp a distinction between the „clypeus" and the labrum proper, as 

 stated by Hansen. The chitinous ridges, which are directed backwards and down- 

 wards from the base of the labium, are much more complicated in their structure 

 than shown in his figure, their connection with the sucking organ I was not able 

 to unravel. The articular membrane of the antennae is probably fastened to the 

 angular line between the "clypeus" and „labrum"'; I think that the latter can be 

 more properly called keeled than compressed. 



The maxillae show a similarity to those of Chthonhis CK.; their hindmost 

 margin is curled over upwards and their terminal or manducatory pari is rounded 

 and bears three hairs in a transverse row (PI. I, fig. 3 a). The lamina maxillaris 

 superior (fig. 3 a. Is) is mounted with a few spines, rounded and almost on the 

 same level everywhere; the lamina maxillaris inferior is larger and prolonged 

 inwards (fig. 3 a, /(). 



The "lyriform organs ' have been described by Hansen (49. p. 208). Near to 

 the inner margin, a little in front of the middle, is found a single strongly curved 

 almost ecliptic fissure, turning the convexity inwards; tliis fissure is not mentioned 

 by Hansen. "Towards the exterior side about a I the middle four large, strongly 

 curved fissures, making together almost a circle" are found according to Hansen. 

 This very remarkable organ is often different in shape at the two sides; in the 

 specimens, which were examined, 1 could not with accuracy count more than three 

 fissures of unequal length. Besides these there are four fissures near the oulmost 

 edge anteriorly. The maxillae of Blolhrns spelaeus Scli. have a peculiar shape as 

 seen in one of Schiödte's figures (31. tab. I, fig. 2d); Ihe median circular lyriform 

 organ is found. 



III. Ideoroncus Balz. (1^1. I, figs. 4 c-f, fig. 5b). 



The labrum of Ideoroncus Siamensis n. sp. is very similar to that of Obisium 

 muscorum Leach. The anterior free portion is rather short; above in the middle 

 there is a distinct keel and a system of chitinous ridges (PI. I, fig. 4 c); the posterior 

 free portion (p) is short and behind fairly rounded, and has several muscles for 

 the sucking organ attached to the ventral surface. 



The maxillae bear similarity to those of Obisium C. K. and have like these 

 the hindmost margin curled over upwards; in the middle they are fused with the 

 labrum for a rather long distance; their manducatory part is moderately pointed 

 and bears two hairs. The lamina maxillaris su]>erior (Is) is longer and more slender 



4" 



