16 Mamm. 
MAMMALIA. 
Noack, T., in Zool, Gait, xxix, pp. 283-285, replies to the criticisms of 
E. Schaff. [See p. 19.] 
Osborn, H. F. The Relation of the Commissures of tho Brain to the 
Formation of the Encephalic Vessels. P. Am. Ass. for 1887, 
p. 262. [Abstract.] 
The author suggests an hypothesis to account for the constant feature 
of the division of the embryonic brain into four swellings or vesicles. 
. The Nomenclature of the Mammalian Molar Cusps. Am. Nat. 
xxii, pp. 926-928. 
Proposes a series of terms for the cusps found in the upper and lower 
teeth of the tritubercular type, which are mentioned under the heading 
of the next paper. 
. The Evolution of Mammalian Molars to and from tho Tritu* 
bercular type. T. c. pp. 1067-1079, pi. xxv. 
After mentioning the importance of the tritubercular type of molar 
structure from a morphological point of view, and referring to its 
frequent occurrence in the Mammals of the Puerco Eocene, and its 
persistence in several existing groups, the author proceeds to divide 
the stages of “ Trituberculy ” into the (i) Haplodont, a modification of 
which is represented by Dromotherium , (n) Triconodont, and (in) Tri- 
tubercular types. The following terms are then proposed to replace 
those in general use for the cusp3 of Mammalian molars, viz. : — 
Upper Molars. 
Antero-internal cusp 
= 
Protocone 
Postero- „ „ or 6th cusp 
= 
Hypocone 
Antero-external „ 
= 
Paracone 
Postero- „ „ 
= 
Metacone 
Anterior intermediate cusp 
= 
Protoconule 
Posterior „ ., 
= 
Metaconulo 
Loioer Molars. 
Antero-external cusp 
= 
Protoconid 
Postero- ,, „ 
= 
Hypoconid 
Antero-internal or 5th cusp 
= 
Paraconid 
Intermediate or antero internal cusp 
(in quadritubercular molars) 
= 
Metaconid 
Postero-internal cusp 
= 
Entoconid. 
The three cusps of Triconodon are considered to represent those of 
Spalacotherium , which clearly correspond to those of the “blade” of 
the tritubercular lower carnassial. 
The paper closes with observations as to the evolution of the cusps in 
various groups, and the transition from a tritubercular to a quadri- 
tubercular type. 
. The Mylohyoid Groove in the Mesozoic and Recent Mammalia. 
T. c. pp. 75 & 76. 
Mentions those genera in which this groove has been examined by the 
author, and concludes that its absence or presence is not of much im- 
portance in classification. 
