458 BULLETIN 10 0, UNITED STATES NATIONAL. MUSEUM 



sal on basal portion. Pair of rostral fins, joined in front of snout, 

 either separated from pectorals or connected with them at side of 

 head. 



Large sting rays of tropical or subtropical seas, feeding chiefly on 

 mollusks, which they crush with their large grinding teeth, though 

 usually less of bottom dwellers than the true rays. In moving 

 through the water they seem to appear as if flying or soaring. 

 Aquarium specimens have been known to utter a rather loud bellow- 

 ing noise when taken from the water. Like the sting rays, these 

 creatures are also dreaded for their murderous spines on the tail, so 

 they are usually removed by the fishermen. All the known genera 

 represented by fossils. 



ANALYSIS OF GENERA 



a\ Myuobatinae. Suout in single lobe ; pelvis arolied. 

 6\ Teeth in more than 3 rows in each jaw. 



c\ Side of head not free from pectorals Holorhinus 



&. Side of head free from pectorals. 



d'. No caudal spine Aetomylus 



(Z-. Caudal spine present Myliobatis 



6^ Teeth in 1 row in each jaw Aetobatus 



c^. Ehinoptekinae. Snout in 2 separate lobes ; pelvis greatly arched. 



Rhinoptera 

 Genus HOLORHINUS Gill 



Holarhimis Gill, Proc. Acad. Nat. Sci. Philadelphia, 1862, p. 331. (Type 



Rhmoptera vespertilio Girard, monotypic.) 

 Myliolatis (not Geoffroy Saint-Hilaire) (Dumeril) Cxtvier, Regne animal, vol. 2, 



p. 13, 1817. (Type, Raja aquila Linnaeus, designated by Jordan and Gilbert, 



U. S. Nat. Mus. Bull. 16, p. 50, 1883.) 

 Myliohates Schinz, Thierreich Cuvier, vol. 2, pt. 19, pp. 234, 832, 1822.— 



(Berthold) Latbeille, Nat. Fam. Tierr., p. 108, 1827. (Type, Raja aquila 



Linnaeus. ) 

 ? Ictaetus Rafinesque, Analyse de la nature, p. 93, 181'5. (Atypic, nomen 



nudum.) 

 T Ptychopleurus Agassiz, Rech. Poiss. Fossiles, vol. 3, p. 67, 1837; Poissons 



fossiles, vol. 3, pi. 45, figs. 1-3, 1838. (Type, Ptychacanthus (Ptychopleurus) 



faujasii Agassiz, monotypic, fossil.) 

 Bates Probst, WUrtembergs Jahresb., vol. 33, p. 88, 1877. (Type, Bates specta- 



Mlis Probst, monotypic, fossil.) 



Disk wide. Tail long, slender, whiplike, strong retrorsely ser- 

 rated spine above base and behind dorsal. Head moderately prom- 

 inent. Eyes lateral. Teeth hexangular, flat, tessellated, in 7 rows, 

 median wider, laterals narrow. Front nasal valves confluent in 

 broad flap with free edge before mouth and joined by frenmii to 

 upper jaw. Spiracles lateral. Skin smooth. Dorsals small, be- 

 tween ventral s. Pectorals slender, falciform, continue along side of 

 head to snout end where joined to form simple lobe. Ventrals short, 

 wide, not emarginate. 



