398 Mr. T. Vernon Wullaston on 



latter the generic name of Mesoxcnus. And, in ])ointof fact, Afe- 

 soxenus and Pentarthnim (each of which have now two known ex- 

 ponents) are remarkably well-defined inter se, and cannot possibly 

 be confounded; for not only has the latter large and fully-de- 

 veloped eyes and a distinct sciitellum (whilst the former is escutel- 

 late, and almost, if not entirely, blind), but its antennte are in- 

 serted, also, mucli further from the apex of the rostrum — which 

 latter is broader, less arcuate, and of j)^''foctl)j equal breadth 

 ihrouglioiit. Tlie Pentarthra, likewise, are more linear, parallel 

 and deeply sculptured insects than the Mesoxeni 'resembling the 

 typical Cussonides), — being less fusiform, and with their protho- 

 races (instead of dilated at the sides) sub-conical. 



The only structural differences that I can possibly detect be- 

 tween the British and Ascension Pentarthra are, that the latter has 

 the joints of its funiculus {vide 19,5 a) a little more compact — 

 with the second one not at all longer than the third (all except the 

 enhirged one at the base being of sub-equal length) — its club 

 smaller, more ovate, and less abrupt, and its third tarsal articula- 

 tion less expanded and bilobed ; but certainly such slight dis- 

 crepancies (which are merely in degree, and not in kind) cannot 

 be regarded, in the present instance, as of more than secondary 

 importance. 



The habits of both of these genera are somevvhat peculiar, their 

 exponents appearing to have a decided partiality for decayed v.'ood 

 in (what one would conceive to be) its least nutritive or attractive 

 state; such as old, used-up planks, rotten boards, and portions of 

 boxes, lying on (and often buried in) the damp earth, and, more- 

 over, as mucli removed from the light as possible. In such posi- 

 tions both of the Mesoxeni were observed (one by Sr. Moniz and 

 the other by Mr. Bewicke) ; as also the Pentartlinun cylindricum, 

 at Ascension; and, to a certain extent, indeed (i. e. amongst cut- 

 up wood in an out-house, and not in the open country), the P. 

 Hultoni likewise. 



32. Pcntarlhrum cylindricum., n. sp. (PI. 19, fig. 5.) 



P. angusto-cylindricum, piceo-ferrugineum, subnitidum, gla- 

 brum J rostro (praesertim in raaribus) latiusculo, in utroque 

 sexu (prsecipue ad basin) sat profunde punctato, lineari, sub- 

 recto, oculis raagnis, leviter prominulis, fronte sub-convexa ; 

 prothorace elongate cylindrico-conico, valde profunde punc- 

 tato, ad latera oblique recto (quare ad basin ipsam, quam 

 alibi latiore) ; elytris sub-rugulosis, striato-punctalis, inter- 

 stitiis minutissime seriatim punctulatis j antennis ad basin 



