MAItVLWI) (IKOI.OIIIC \L Sll{\i:V KJ I 



til llif (iiiLiiiial, which is the l;ir;:cst siicciiiini hitlicrto rcjitntrd from 

 this (•(Hiiilry. 'I'hc (inured spccinicii Wiis I'diiiKl sil Aslih'V, Soiilh ("aro- 

 liiia, and is preserved in ihe .Mii>enni nf ( '(ini|iai'at ive Zooloiiy at ("aiii- 

 hridi;c, Mas.-aehnselts. Tlie >li-(in,i:- eiii\alni-e n\' the oi'al siirracf. wliicU 

 is einial ill l)()lh lon^it iidinal and t i'an.-\ I'l'-e dii'eciions. togctlier with 

 the |ii(i|)iii-| itms and wavv sntiires n\' the median teeth |ti'()ve it beyond 

 all (hiid)( In he thi' nppei' ih'niiliiin. |ii'e\-i(Misly unknnwn. cd' a s|)ecie8 

 innnded liy Leidy nn a iniii|Ue lower (h^nlal plate fi-nni the same locality, 

 to which he applieil the name .1/. iikii/IsIit. l^'idy himself, and follow- 

 ini:' him A. S. W'dndwai'd. were n\' the opinion that the type-specimen 

 nueht I'epreseid the lower (h'lilition of .1/. Iidliiifsii (lihlies. winch was 

 dc'scril)('d from a supposed nppei' dental plate with sti'onnly curved su- 

 tures. The specimen in the ( andu-idiie collection, however, completes 

 our knowledg-e of the dentition of d/. magister, and we must look else- 

 where for the opitosing dentition of (iibbes' species. The latter, as has 

 already been intimated, a])pears to be only very sliulitly dilTerent fi'om 

 j\I. copeanus of this state. 



TJie type consists of a lower dental jdate. 



CoUedions. — Philadelphia Academy of Xalural Sciences, Museum of 

 Comjiarative Zoology, Candjridge. 



Genus AETOBATiS Miillcr and Henle. 



In this genus there is but a single series of very broad, flat teeth, 

 those of the upper jaw only ditfering from the median teeth of Mylio- 

 hdtis in their truncated lateral ends. The lower dentition is very nearly 

 flat, and the teeth are all more or less strongly curved or angularly bent 

 in the middle. The coronal surface is smooth or slightly striated, and 

 the attached surface of the root longitudinally ridged or grooved. 

 AVoodward ' remarks that '" In this genns there is much less variability 

 in the relations of the length and breadth of the teeth according to age 

 than in Myliobatis ; but the form of the lower teeth is so inconstant, 

 that species cannot be determined upon the evidence of the lower denti- 

 tion alone." 



' Cat. Foss. Fishes, British Jfuseum, pt. i, 18S9, p. 128. 



