River Sturgeons of the American Genus Scaphirhynchus: Characters, Distribution, and Synonymy

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Sturgeons of the Genus Scaphirhynchus 193 stuffed skin without a label, probably specimen e (Gunther, 1870: 345). She reports that this specimen agrees exactly with Gray's de-e"intion in plate counts and other details. The fish reported from New Orleans (Gunther, ibid., spirit specimen c, number 1852.8.16.26) was also examined by Dr. Trewavas, who has provided the following measurements, taken by the methods employed in this paper: Type specimen mss"b� x fi of Acipenser New Orleans Measuremeni cataphracius specimen (in (in t mm.) mm.) zks� Standard length ca. 484 440 110.5 IIead length 144.5 Snout tip to inner barbel 48.5 40s Inner barbel to front of mouth 49.5 31 w ' Inner barbel ca. 45 43.5 n Mouth width ca. se 30 Z# *r !'�cpth of tenth lateral plate 19.5 14.5 into ratios listed in Table IV, these measurements yield the following values: ratio 1, 1.09 and 0.97; ratio 3, 4.15 and 3.56; rr t;o 6, 4.90 and 4.70; ratio 9, 6.28 and 8.84. Reference to Table IV makes it obvious that both specimens are Scaphirhynchus platoryn- chus. This verifies the allocation of Acipenser cataphractus to ti:e senor• ^ y of that species and provides the only acceptable record of 1,. ':us from the lower Mississippi River. r;'s (1836) Scaphirhynchus rafanesquii, without specific local- . ity, is referable to the synonymy of the more common species (S. platorynchus), as is evident from the careful original descript �.. , ..0 the excellent drawings that clearly portray such diagnostic features as the barbels and the midventral plates. Giltay (1929) proposed the name Scaphirhynchus mexicanus on the basis of a single mounted specimen from Mexico, or perhaps Texas. His characterization depends on the supposed intermediacy in size of the ventral scutes; but there is much variation in these structures in platorynchus. The short inner barbels attributed to mexicanus agree in length better with those of S. album, but in Gil- t: -Y's motwted specimen, which had been caught at least seventy ,N-ear i,e.or,, their original length could not have been ascertained. Unfortunate] standard length was not recorded, so accurate inter- pretation of the other measurements is impossible. The photographs ;