Fishes of the Western North Atlantic 397 



Pteroplatea Miiller and Henle, S.B. Akad. Wiss. Berl., 1837: 117; no species named; Plagiost., 1841: 168; 



type species Raja altavela Linnaeus 1758, designated by Jordan (Genera Fish., 2, 1919: 193). 

 Pastinaca (in part) DeKay, Zool. N.Y., 4, 1842: 375; for Raja maclura Lesueur 1817. 

 Dasyatis Gray, List Fish. Brit. Mus., i, 1851 : 121; type species, D. altavela Gray, equals Raja altavela Lin- 

 naeus 1758.^ 

 Ceratoptera Day, Fish. India, I (4), 1878: 745, fig. not numbered; for C. ehrenbergii Day (not Miiller and 



Henle 1841), a monstrosity oi Gymnura, probably G.poeciltira (Shaw) 1804.* 

 Astrape (in part) Day, Fish. India, Suppl., 1888: 812; substituted for Ceratoptera Day 1878 on the incorrect 



supposition that the latter was a monstrosity ol Astrape dipterygia Miiller and Henle 1841, one of the 



Torpedo Rays. 

 Pteroplataea Alcock, Ann. Mag. nat. Hist., (6) 9, 1892: 419; emended spelling for Pteroplatea Miiller and 



Henle 1837, 1841. 

 Planerocephalus Grazianow, Zool. Anz., JO, 1906: 400, 403; new name to replace Ceratoptera Day 1878; 



see above. 

 Phanerocephalus Grazianow, Zool. Anz., JO, 1906: 404; emended spelling for Planerocephalus Grazianow; 



type species, P. elltoti Grazianow. India. 

 Not Dasyatis Rafinesque, Carratt. Gen. Spec. SiciL, 1810: 16; see p. 340. 

 Not Gymnura Miiller and Henle, S. B. Akad. Wiss. Berl., 1837: 117; see p. 396, ftn. 3. 

 Not Ceratoptera Miiller and Henle, S.B. Akad. Wiss. Berl., 1837: 118; Plagiost., 1841: 186; equals Manta 



Bancroft 1828-29, ^^'^ P- 5°I- 



Generic Characters. No dorsal fin. Characters otherwise those of the family. 



Developmental Stages.'' While both reproductive organs are functional as a rule, 

 the left ovary is usually better developed and has the larger number of eggs. Instances 

 have been recorded in which the left ovary alone contained eggs. Ordinarily one 

 embryo develops in each oviduct, but occasionally two or three, and at least one case 

 of polyembryony (two yolks within a single shell) has been observed.* Before the 

 embryos are born, ovarian eggs that presage the next generation have been recorded 

 as reaching a diameter of 5 to 10 mm. The length of the period of gestation is not 

 known. During the early stages of embryonic development the egg is enclosed in a 

 thin straw-colored membrane that is more or less folded or plaited at the ends; the 

 embryo is set free from this into the uterus while it still has external gill filaments and 

 yolk sac. The young, after liberation into the uterus, are nourished partly by the con- 

 tents of the yolk sac but largely by the fluid secreted by the glandular villi with which 

 the inner uterine walls of the mother are densely clothed. Elongated clumps of these 

 villi extend into the spiracles of the embryo, which is evidence that it takes in the 

 "milk" via the spiracular openings; perhaps it also takes the "milk" through the mouth 

 and by absorbing it in early stages through its free gill filaments.^ Advanced embryos, 



5. Gray characterized his Dasyatis as having a disc nearly, or more than twice, as broad as long and the tail mostly 

 shorter than the body; species included were altai'ela, canariensis, micrura and maclura. 



6. This was a monstrosity of the same sort that has been reported for various Skates and Rays in which the anterior 

 parts of the pectorals fail to unite with the sides of the head, hence have the form of narrow secondary lobes directed 

 forward. 



7. Knowledge of the developmental stages of this genus is due to observations by Alcock and Wood-Mason (Proc. 

 roy. Soc. Lond., 4g, 1891: 364; 50, 1891: 203); by Gudger (Science, N. S. 33, 191 1: 943; Proc. biol. Soc. Wash., 

 25, 1912: 149; Proc. biol. Soc. Wash., 26, 1913: 100) as Pteroplatea maclura; and by RadclifFe (Bull. U. S. Bur. 

 Fish., 34, 1913: 277). 



8. By Gudger (Proc. biol. Soc. Wash., 26, 1913: 100, as Pteroplatea maclura), who also lists references to polyembryony 

 in other elasmobranchs. 



9. Knowledge of the relationship between mother and embryo in Gymnura and of the embryonic nutrition is due 



