90 Bulletin ^7, United States National Museum. 



California from Cape Mendocino southward ; very common along mud 

 flats. Destructive to oysters. 



nhinoptera vespertilio, Girard, Proc. Ac. Nat. Sci. Phila., 185G, 137, Tomales Bay; not Mijlwbatis 



vesperlilio, Bleeker, also a MyliobatU<. 

 Holorhinus vespertiUo, GliJ., Proc. Ac. Nat. Sci. Phila., 1862, 331. 

 Mi/Unhatis ealifomicHs, Gill, Ann. Lye. Nat. Hist. N. Y., 18G5, 137, (after Girard). 

 MiiUubatis californkus, Jordan & Gilbert, Syuopsie, 51.1883. 



57. RHINOPTERA, Kuhl. 



Rhinoptera, (Kuhl), Guvier, Eogne Animal, Ed. 2, 1828, (marginata). 

 Zyijohalis, Agassiz, Poissons Fossiles, m, 79, 183G, (jtissieui). 

 Mylorhina, Gill, Ann. Lye. Nat. Hist. N. Y., 1805, 136, (Mandi). 

 Micromesus, Gill, /. c, {adspersm). 



Disk broader than long, with the anterior angles more or less acute. 

 Snout more or less eniarginate on the median line. Cephalic fin emar- 

 ginate and placed on a plane below the level of the jiectorals, the snout 

 thus appearing 4-lobed. Free border of the nasal valve not emarginate. 

 Teeth in 5 to 20 rows, the median teeth enlarged or not, but often smaller 

 than in Ceplialeutherus. Tail long, whip-like, with a small dorsal fin and a 

 serrated spine. Tropical seas. The species vary considerably in their 

 dentition. (p/iJ, snout; Trrcpov, fin.) 



Rhinoptera: 



a. Teeth of middle of upper .jaw much broader than those of sides, the lateral teeth gradually 



diminishing. 



h. Teeth in 7 rows ; the median teeth above about 4 times as broad as long ; breadth of disk 



X}^ times its length. bonasu.s, 135. 



hh. Teeth in 7 rows, the median teeth 3% times as broad as long; breadth of disk 1|J^ 



times its length. steindachneri, 136. 



MicnoMESi'S (niKpds, small; /uecro?, middle): 

 aa. Teeth of middle of upper jaw not much larger than the outer teeth; teeth in many series. 

 c. Teeth of lower jaw in about 15 series; the teeth unequal but all small, the broadest 

 being those of the 6th to 8th series from the side which are twice as broad as long. 



ensenada;, 137. 



Subgenus RHINOPTERA. 



135. RHINOPTERA BONASUS, (Mitchill). 



(CoW-NOSE KaT.) 



Disk i broader than long; anterior borders almost straight, posterior 

 undulated; muzzle deeply emarginate; teeth in 7 rows in each Jaw, the 

 median teeth above 4 times as broad as long, the others gradually dimin- 

 ishing outward. Tail very slender, a little longer than the disk. Skin 

 smooth or nearly so. Color brownish. Cape Cod to Florida; not rare; 

 feeds on mollusks.* {bonasus, bufl'alo.) 



liaja honasiif, Mitchill, Trans. Lit. and Phil. Soc. N. Y., 1815, 479, New York. 



Raia qnadriloha, Le Sueur, Jour. Ac. Nat. Sci. Phila., i, 44, 1817, New Jersey. 



Rhinoptera quadriloba, GCntiier, Cat., viii, 494,1870. 



Rhinoptera quadriloba, Dum£bil, Elasmobranches, 648, 1870; Jordan & Gilbert, Synopsis, 51, 1883. 



* " He enters the bay and ranges very extensively on the flats where the soft clam lives. These 

 shellfish ho is supposed to devour, for a slioal of cow-noses root up the salt-water flats as com- 

 pletely as a drove of hogs would do."— Mitchill. 



