uniform. The unusual development of the second joint of the maxillary and the 

 labial palpi distinguishes the Corylophida from many other families, and prevails, 

 with trilling modifications, through all the genera ; although in the maxillary 

 palpi of Siirium and ArthnAipx this character is somewhat evanescent, yet in their 

 lahial palpi it becomes so strongly developed that these organs present the appear- 

 ance of small circular plates attached to tlie anterior extremity of the labium, and 

 it is only after immersion in Canada balsam that their true character can be ascer- 

 tained. In these two genera, and indeed in almost all the Corylophidce, the organs 

 of the mouth are so exceedingly delicate and fragile, that their dissection is a far 

 more diflficult operation than it would be in the case of the smallest Trichopterygian. 



The two curious genera, Aphanocephalus and Phcenocephalus, discovered by 

 Mr. Lewis in Japan, and described as Coryhphid(e by Mr. Wollaston, differ so 

 widely in many essential points from the Corylophide type that a mere tribal 

 separation becomes wholly inadequate. Aphanocephalus exhibits, instead of the 

 normal uuilobed maxilla, a maxilla with three separate lobes, resembling the 

 maxilla of all the TrichopU'rygidd except in this one point — that the outer lobe, an 

 integral part of the stipes, is not placed, as in the Trichoptcrygidce, on the same 

 level as the true lobes, but rises from the middle of the outer disc of the stipes, 

 and does not extend for more than half of its own length beyond the base of the 

 other lobes. This lobe is vei-y conspicuous without dissection in the mouth of any 

 Aph a n oceph alits. 



The stipes itself, which in the true Coryloplt'uhe is always small, sometimes 

 almost rudimentary, is in this genus as long and as large as it is in the 

 Trichopter/ifiidce. Again, in the rounded and wholly enclosed anterior coxae, and in 

 the enormous size of the mesosternal epimera, Aphanocephalus assimilates the 

 Trichopterygidce ; but in the shape and disposition of the coxal cavities it is unlike 

 that family or the Corylophida ; the same remark also applies to its antennae, 

 whose club appears to consist of a single articulation, and, although the separation 

 of the joints ma}' be discerned under a high power, at first sight it much resembles 

 the solid club of Sphceriun. In Aphanoccplialiis all the tarsi are distinctlj' three- 

 jointed, without any trace of the usual small penultimate joint ; its wings are also 

 formed on a very different plan, and in shape and neuration resemble the wings of 

 the Silphidce. In short, the large size of the first ventral segment is the only 

 Corylophide character in the skeleton of Aphanocephalus, although some affinity is 

 shown in the shape of the palpi and some other organs of the mouth. It is, 

 therefore, impossible to retain Aphanocephalus among the Corylophidce ; and, since 

 the genus cannot be placed in any other family, I have designated its species as 

 Vscudocoryloph idee. 



An almost similar isolation occurs in the case of Ph(enoeephalus ; for, while 

 it possesses no single character in common with Aphanocephalus, its bilobed 

 maxillic and Silphide posterior coxae effectuallj' prevent its association with the true 

 Corylophidw. The only practicable course to pursue is to consider the genus as a 

 distinct family in itself. 



