^%tiy''] PROCEEDINGS OF THE NATIONAL MlISErM. 27 



189:3. 



L<)\Vi:it MOLAKS. 



AntiTo-external cus\> rrotoconid. pr'' 



Postero-exterual fusp Hypocoiiid. liy' 



Aiitero-intenial cusp or liftli i^u.sp Paracouid. ]ia'' 



Intormediateorantero-internalciisp (in (iiiailritultiMciilar molars).. Metaconid. me'' 

 Postero-iiitoriial ciisj) Eiitoroiiid. en'' 



The u])i)er molar in most bats presents to an extraordinary degree 

 depressions on the outer or buccal surface of the crown. Such dei)res- 

 sious receive the name of "tlutiugs" and are seen in the teeth of many 

 mammals other than the bats, as for example in the moles and shrews 

 among the Insectivora, in the LTugulata, and in a. marked degree in au 

 extinct genus described by Prof. Cope, Lamhdotherhnn. "Flutings," 

 while of no homological significance, furnish systenuitic characters, and 

 will therefore be noted in the descriptions. Disposed so as to define 

 two V-shaped figures the "flutings" extend as a sinuate commissure 

 between the paracone and the metacone. Of the twoVs an anterior 

 and a posterior will be distiuguished. Each V has two limbs, a first and 

 a second. In the third molar various degrees of loss of the system 

 of tiutings occur. Commonly the anterior V is retained while the sec- 

 ond is lost, excepting the buccal half of the first limb, as in V fuscus, or 

 the ''fluting'' is reduced to the anterior V, the palatal half of the sec- 

 oud limb being lost, as in Marrotufi and Atalapha. In the Bats of North 

 America the least reduced last molars are seen in Nyctinomus and V. 

 hesperuH. 



The tri-tubercular tooth which results from the presence of the three 

 cusps, the i^rotocone, the paracone, and the metacone, may be con- 

 'lected with a triangular figure by bands which unites the cus])-points. 

 ^hese bands will be named in this monograph the commissures. In the 

 molars of the bat such a triangle is seen whose apex is x)alatal and 

 constituted of the protocone and whose commissure extends from this 

 cusp to the paracone and metacone. Its base is the extraordinarily 

 sinuate (''fluted") buccal surface of the crown. A careful search must 

 be made for tlie true positions of the sides of this triangular figure for 

 they lie on the opposed sides of the teeth and are inconsi)icuous. The 

 crown at the " flutings" is of great vertical extent and dwarfs even the 

 proportions of the protocone. When seen in profile the proportions 

 between the size of the "columns" of the two V's and the "cusp" of 

 the protocone aftbrd materials for interesting comparisons in the differ- 

 ent genera. The hypocoiie presents excellent subordinate characters. 

 It is a development of the cingulum. Usually flat, as in Macrotm, it 

 may be a sharply defined as in Priymopsperotis, or provided with a sharp 

 cusp as in the exotic genus Nociilio. The cingulum can be traced as a 

 delicate ridge which lies basal to the sides of the tritubercular triangle. 

 It varies greatly in extent, being best developed in JifycUnomns. 



In the lower molar scarcely any fluting is present and the plan of the 

 tooth is simple. The protoconid, paraconid, and melacouid are united 



