TRrGONID^. 
163 
was first figured by Volta', under the name of Raja muricata, and 
subsequently assigned to Trygonohatus vulgaris by de BlainviUe 
The same specimen was afterwards named by Agassiz * Trygon gaz- 
zolce ; and more recently Molin ' and Baron de Zigno ‘ have founded 
the genus Alexandrinum upon a very similar fossil, which is not 
clearly distinguished either by the figure or in the descriptions. 
A second species was described by de BlainviUe (loc. cit.) as Trygo- 
nobatus crassicaudatus, and likewise re-named by Agassiz (loc. cit.) 
Trygon oblongus. 
The small fragment of tail, with caudal spine, originally figured 
upon Volta’s plate of “■Raja muricata” has been identified with 
other more recently discovered specimens considered by Heckcl ® 
and Molin to he referable to Tceniura, and accordingly named 
T. hnerii. 
Another Monte Bolca fossil has been described by Molin “ as re- 
ferable to Anacanthus, Ehrenb. (= Urogymnus, Miill. & Henle), and 
named A. zigni. Neither this description, however, nor Baron de 
Zigno’s subsequent figure * appears to place the generic determina- 
tion beyond doubt. There are no dermal asperities such as specially 
characterize the living Urogymnus, and it seems quite possible that 
the brevity of the tail and the absence of caudal spines may be 
merely due to accident in preservation. 
The New Zealand fossil teeth and spines named Trygon ensifer, 
J. W. Da'sds (Trans. Boy. Dublin Soc. [2] vol. iv. (1888), p. 37, 
pi. vi. figs. 13-15), are evidently not Selachian. Equally doubtful 
also is the so-called Trygon pastinacoides, van Bcneden (T. C.Winkler, 
Archiv. Mus. Teyler, vol. iii. 1874, p. 304), from the Bruxcllian 
Eocene of Belgium. 
Genus XIPHOTRYGON, Cope. 
[Amer. Naturalist, vol. xiii. 1879, p. 333.] 
Syn. Ileliobatia, O. C. Marsh, Amer. Journ. Sci. [3] vol. xiv. 1877 
p. 266 (undefined). 
Distinguished from Trygon by the cuspidate character of the teeth. 
* Ittiolit. Veron. 1706, p. 37, pi. ii. fig. 1. 
= Nouv. Diet. d’Hist. Nat. vol. xxvii. (1818), p. 336. 
’ Neues Jahrb. 1835, p. 297. Poiss. Foss. vol. iii. p. 382**. 
* SiUungsb. math.-nat. Cl. k. Wiss. Wien, vol. xlii. (1861), p. 579. 
' Mem. B. Istit. Veneto, vol. xviii. (1874), p. 299, pi. xii. (A. molinii). 
‘ Sitzuiigsb. math.-nat. Cl. k. Ak. Wiss. Wien, vol. vii. (1851), p. 324. 
’ Loc. cit. vol. xlii. (1861), p. 581. » Ihid. p. 578. 
' Mem. R. Istit. Veneto, vol. iviii. (1874), p. 298, pi. xi. 
