1852.] } 37 
necessity of proposing important modifications of the arrangement adopted by 
him.* 
The great increase in the number of our species, since the publication of the 
monograph of Histers by my father,t has made me acquainted with many varia- 
tions of structure, too unimportant to serve as foundations for separate genera, 
yet absolutely incapable of entering any of the genera established by Erichson. 
Some of these anomalous species have been described by me in the Annals of the 
Lyceum of Natural History, vol. 5. 
By a careful comparison of such forms with the species to which, by obvious 
characters, they are most nearly allied, I have been led to believe that the genera 
in this group have been unnecessarily increased, by the use of principles of 
division which are by no means of generic value, and which scarcely serve to 
define small groups of species. 
I allude more especially to the structure of the tibiew, which holds so important 
a place in the system of Erichson. The difficulty of deciding upon such an indis- 
tinct character as the form of the tarsal groove of the anterior tibiew, and the 
decidedly variant structure of the posterior tibiz in several of the genera, has 
led me to reject entirely the characters drawn from those parts of the body. The 
special variations referred to will be exposed more fully under the genera Hister 
and Saprinus below. 
Following Erichson, I have divided the genera into three groups according to 
the position of the head and the form of the prosternum. The genera may after- 
wards be separated according to the following table: 
4. Caput porrectum: prosternum antice non lobatum. 
Mandibulz dentate ; : 4 5 : : - Hotorerta Payk. 
Mandibule dentate, prosternum latum planum - 1PuHyztioma Er. 
Mandibulez dentate, prosternum elevatum, subacu- 
minatum : : é . : ° ° - 1OxysTEeRNUsS Er. 
B. Caput retractum; prosternum antice valde lobatum. 
a. Scrobiculi antennales antici. 
1. Tarsi antici unguiculo unico - : . ‘ - 1Cyprurus Er. 
2. Tarsi omnes biunguiculati. 
Mandibulz porrecte, antenne sub frontis margine inserta, 
capitulo 3-articulate : : : 6 é . 2 Arster Linn. 
Mandibule porrectz, antenne sub frontis margine insertz, 
capitulo solido, truncato . : ° : - 3HeTzrivs Er. 
Mandibule retract, antenne in frontis margine inserte, 
capitulo 3-articulato, rotundato, . 6 - Epierus Er. 
Mandibulz retracts, antenne in frontis margine inserte, 
capitulo 3-articulato, truncato : : ° . YRiBatus Er. 
b. Scrobiculi antennales medii, laterales, 
Antenne articulo 8vo latiore : 4 6 . - DeEnpRopHituS Leach. 
Antenne articulo 8vo non latiore : 6 D - Paromatuus Er. 
C, Caput retractum, prosternum antice non lobatum. 
a. Antenne sub frontis margine insertez. 
Mandibulz exserte; scrobiculi antennales antici - C#ROSTERNUS DN. g. 
Mandibule exserte; scrobiculi antennales ad prosterni 
latera siti : : : : : : : - 4Saprinus Leach. 
Mandibule clypeo obtecte . - 5 : : - 1TRyponaus Er. 
* Klug’s Jahrbticher fiir Insectenkunde. 
J Boston Journal of Natural History, yol. V. p. 32. 
1 No North American species. 
2 Including Omalodes Er.; Platysoma Leach, Er; (2?) Plesius Er. and (?) Placodes Er. 
I have not examined the last two'genera, but the description furnishes no good charac- 
ters for separating them. 
3 Hister brannipennis Rand., and a new species, + Including Pachylopus Er. 
