228 GOMPIIUR OILATATUS, VASTUS AND LINP^ATIFRONS (oDONATA) 
Gomphus vastus Walsh 
It will be noticed that dilaiatus as a])Ovc defined is very similar 
to the foi'in known in onr literature as Gomphus vastus Walsh. 
l)e Selys, in redeseribinjj; vastus in IStit), said of it: ‘‘Excessive- 
numt voisin dn (Ulatatus. II en diflcre principalement par la 
taille moindre,”-’ remarks rvhieh would be far less appropriate, 
ai)i)lied to the northei'n form wdiieh has passed as dilatatus and 
which it is now pi'oposed to call It neatifrous. Most of the dif- 
f(‘i-(mc('S which ai'e ji;iven above to sepai-ate liucatifrous from 
dilatatus will also S(‘rv(‘ to distinguish liue(difrous ^yon\ vastus. 
]'aslus differs from dilat(dus as follows fusing the same numbers 
foi' the diff('rentials as above): 
2. Width of the black band on the fronto-nasal suture absolutely less 
(.() to .74 nun.) and relatively narrower, occupying less than half the height ol 
the front and less than halt the height of the nasus. 
10. Pah' inarking (yellow) on the niiil-dorsum ol al)donunal segment 
sev('n snuiller, n'aching from the aid('rior ('iid to tWo-filt hs or to one-halt t)i 
I lie segment.’s length. 
1-t. Size smaller: abdona'ii cf '47 to 41, 9 44 to 41; hind wing cf 20 to ol, 
9 ‘4 1 to 44 mm. 
20. 9. Hind margin of the occiput, in antero-suiierior view, mori' widely 
(‘xcavated even than in /<«cr////’/7ues, showing no slight convc'xitj’ between tlu' 
nu'dian ('inarginat ion and (‘a(4i lateral ('xtremity such as is visible in our 
ligure :t, Plate .\l\’; in dorsal view bent more “foi'ward in the miildle,” as 
Walsh noted in his original description, than in either tliliildlus or hneali- 
J' r on x. 
21. cf. 4'ooth of the penis more slender, more ai'iite (cf. I’late X\ . figs. 
21, 2:1). 
22. 9- A conical spim* on the V(‘rtex bctwec'ii ('ach latc'ral ocellus and 
the adjoining eye, absent in tlilolotiis ;ind in liiicolifroiix (cl. Plat('X 1\ , hgs. 
to 7). 
.\mong the material of roshis which 1 hav(' ex.ainiiu'd is a female Irom' 
Puckingham ('ounty, \ irginia, Juiu' 21, 1010, coll('ct('d by Mr. W m. 4'. 
Davis and in his collection. Both Mr. Davis and 1 had, at hrjst, n'ferred it 
to (lil(il(ilu.'<, but I now believe' that k is voslus, as it. agre'i's with the latter 
in the distinctions just given umh'r numlx'rs It) and 22. It is largc'r than 
any other m.s7//.s that 1 have seen or whose' elime'iisiems are' given in the lite'i- 
al lire', viz. : abilome'ii 1 1, hind wing .4."). 5 mm. ; it is still smaller than the small- 
est fe-male' eif ditohihis. Its eie-eaput (fig. b), ein the' eithe'r hanel, is ne'are'r to 
that of (liliiloliis than tei that eif /’e;.s7//.s', while' its blae'k fronto-nasal hanel is 
narrowe-r (.1 mm.) than in e-itln'r. 
All llie'se' f.'icls, l()g('l lu'r with its locality suggt'sl llnit more' 
muH'i i.'d e'eelle'e'le'el be-t we'e'ii \'ii-ginia anel (le'orgia may show vastus 
' Bull. .Aeaid. Boy. Be'lg., (2) xxvui, p. 177, eer 2ele's .\ilelit. Svn. (hemph., 
p. 14. 
