1853.] 275 
which have an appearance of being truly natural, that I have not considered it 
prudent to adopt their views. 
Among some of these groups, (e. g. S. lapponica, 8. americana and S. ramosa,) 
appear several forms, which are undeniably distinct in their origin and distribu- 
tion and yet do not present characters sufficiently definite for their perfect 
separation. Many genera among more highly organized animals presenting 
this same peculiar specifie relation will occur to the mind of every naturalist, 
but this is, I believe, the first example distinctly noticed among Articulata ; 
nor can | find in scientific memoirs any allusion to a doctrine, which flows very 
naturally from such observations, viz: There are in nature genera so constituted 
that their division can naturally be made only so as to exhibit assemblages of 
individuals, which are multiple and distinct in their origin, but which are so 
closely related that any attempt to define and isolate them must result in con- 
fusion. The interpretation of so called geographical varieties, is obviously a 
portion of this doctrine ; but for the present, I must merely content myself with 
this brief notice of a view, which, whether it be eventually proved correct or 
erroneous, might ere this have exerted a beneficial influence upon certain por- 
tions of Natural History, where the zeal for creating irrecognisable species has 
been pushed to a prodigious extent. 
Div. 1. Silphales genuini. 
Trochanteres postict fulcrantes ; cox@ postice approximate.* 
NecrorHorus Fabr. 
A. Thorace convexo, tenuiter marginato, antice non impresso. 
1. N. mediatus, niger, thorace obovato, antice dense punctulato, lateribus 
et basi punctato, elytris macula humerali, altera transversa ante medium, 
tertiaque lunata versus apicem rubris; antennarum clava ferruginea; pectore 
abdominisque basi ad latera auropilosis. Long. -&7—-95. 
Fabricius, Syst. El. 1, 334: Latreille, Gen. Ins. 2, 5. 
Southern States, Missouri Territory and Texas. This very distinct species 
differs from all the succeeding ones by the epipleure being narrower, less in- 
flexed, and less distinctly margined above. The posterior tibia are very much 
dilated at their extremity. In the male, the anterior tarsi are only moderately 
dilated, and the yellow hair at the base of the abdomen is more abundant. In 
both sexes the rhinarium is triangular. 
Among ‘the specimens from Nebraska are varieties in which the anterior 
transverse spot is divided; in some the outer part of this divided spot is effaced; 
in such individuals the posterior lunate spot is much reduced in size. 
B. Thorace antice transversim impresso, margine laterali anguste depresso. 
2. N. marginatus, niger, thorace obovato, marginibus parce punctulatis, 
lateribus vix sinuatis, elytris lateribus, fascia communi ante medium, alteraque 
utrinque subapicali rubris; antennarum clava ferruginea; pectore aurapiloso. 
Long. -57—-88. 
Fabricius, Syst. El. 1, 334. 
New York, Georgia, Texas, Nebraska and California. The rhinarium is red 
and triangular; the posterior fascia does not entirely reach the suture, and its 
outer portion is contiguous to the apical margin. The anterior band is some- 
times interrupted towards the side, and sometimes one of tts posterior dentations 
is prolonged so as to reach the inner part of the posterior band. The anus and 
margins of the abdominal segments are ciliate with black hairs. The anterior 
tarsi of the male are moderately dilated. 
3. N. Melsheime ri, niger, thorace obovato, lateribus subsinuatis marginibus 
punctatis, epipleuris elytrorumque facilis utrinque duabus dentatis rubris; anten- 
narum clava ferruginea, basi nigra, pectore anoque flavo-pilosis. Long. -92. 
* This last is a character found in the whole group; it is merely added here 
for the convenience of those who may desire to consider Scydmenide as a 
division of this, and not a distinct family. 
