A treatise on zoology . ian Ocean, to Eocene,Europe. Hypnos, Dum. ; Australian. Narcine, Henle ; troj^ical seas, andEocene, Italy. Astrope, M. and H. ; Indian Ocean. Temera, Gray ;Indian seas. Group C. Centrobatoidei. The rostral cartilage is usually lost, but the skeleton of the pec-toral fins grows forward to meet in front of the skull (Fig. 119, B). i64 SELACHIl The tail becomes very distinctly marked off, and slender; the singledorsal fin which alone remains not moA-ing down towards the tip ofthe tail, but being situated near its base. The pelvic girdle hasa median and no lateral prepubic
A treatise on zoology . ian Ocean, to Eocene,Europe. Hypnos, Dum. ; Australian. Narcine, Henle ; troj^ical seas, andEocene, Italy. Astrope, M. and H. ; Indian Ocean. Temera, Gray ;Indian seas. Group C. Centrobatoidei. The rostral cartilage is usually lost, but the skeleton of the pec-toral fins grows forward to meet in front of the skull (Fig. 119, B). i64 SELACHIl The tail becomes very distinctly marked off, and slender; the singledorsal fin which alone remains not moA-ing down towards the tip ofthe tail, but being situated near its base. The pelvic girdle hasa median and no lateral prepubic process. Family Trygonidae. The large rhombic disk is completed in frontof the skull by the pectoral fins, which meet in the middle anterior axis rests on the preorbital process. The skeletal rostrumis represented only by a median strand of connective tissue (Fig. 119).A slender horseshoe-shaped basihyal is present ; but the basibrauchialsare fused into a single large plate, apparently together with the hypo-. Fig. 1-27. Dorsal view of I^teroplatea Faleneicnnii, Duiii. (after Gannaii), showing the extensivedevelopment of the lateral-line organs, de, endolynipliatic openings ; pv, pectoral tin ; ph;pelvic tin; sc, spine ; sp, spiracle. branchials. The ceratohyal is attached either to the skull directly orto the base of the hyomandibular. The stout transverse jaws heavnumerous small and usually sharp teeth. The tail is slender, varyingmuch in development. In Urolojjhus it bears a terminal fin, andin Trygonoptera a dorsal fin ; but as a rule it is whip-like, and haslost almost all trace of the fins. On the other hand, it is generallyprovided with one or more large serrated spines (Fig. 127), whence theirname Sting-Rays. These spines are placed behind the fins, not in frontas in other Selachians. Xyphotryrjon, Cope ; Eocene, N. America. Urolophus, M. and H., andTrygon, Ad. ; warm seas, and to Eocene, Italy. Uroyymnus, M. and H.;Indian seas. Pterojjlatea, M. and H. (Figs.
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectzoology
