TOXOCHELYID^. 



I 79 



the latter two peripherals are slightly wider proportionally than are those of T . bauri. As 

 regards the thickness no definite statements can be made about either species, but both appear 

 to resemble the corresponding peripherals of Lytoloma. 



The carapace of T. bauri has a length of about 530 mm. ; its greatest width, when restored 

 to what is regarded as its original form, is about 400 mm. The species was therefore of consid- 

 erable size and the form was relatively narrow. In front the outline is concave along the nuchal; 

 while the rear is rounded. There are no excavations over the anterior limbs, such as are seen 

 in the modern Cheloniidae. 



This carapace is composed of 8 pairs of costals, a nuchal, 9 neurals, apparently 3 suprapy- 

 gals, a pygal, and II pairs of peripherals. The first, second, and tenth peripherals had no 

 connection with the costals. The others received each the extremity of a rib in a pit. In all, 

 except the third and the eleventh, this pit is nearest the hinder end of the peripheral. There 

 are large costo-penpheral fontanels, which extended from the peripherals half-way to the 

 neurals. Besides these vacuities, there is a small one on each side at the common meeting- 

 place of the nuchal, the first costal, and the first neural. Similar vacuities are found in a few 

 of the Trionychidae. 



The accompanying table shows the dimensions of the neurals, taken from Wieland's 

 description of the species. The forms may be determined from fig. 229. 



Neural. Length. Width. 



38 

 44 

 44 

 46 



34 

 5 

 40 



*5 

 '5 



38 

 37 

 4 

 44 

 45 

 4 

 38 

 35 

 35 



FIG. 230. Toxochelys bauri. Shell presenting left side. Xn- 



/, fontanels behind the nuchal; s, s, s, series of ossicles surmounting certain of the 

 neural bones. Reproduced from figure by Wieland. 



It seems evident that an extra neural was intercalated in the series. This is shown by the 

 fact that, as the series runs, most of them are crowded somewhat out of their natural positions, 

 being nearly as much in contact with the costals in front of them as with those to which they 

 belong. This intercalation is shown in another way. There is a series of ossicles, 4 in number, 

 along the midline ossicles which Wieland calls epineurals. The first forms a slight boss on 

 the first neural. The second lies across the suture between the third and the fourth neurals; 

 the third, across the suture between the fifth and the sixth neurals; the fourth rests on the 

 eighth and ninth neurals and the first suprapygal. This arrangement does not agree with 

 that appearing to exist in the other specimens of this genus which have furnisht the neurals. 

 Moreover, it does not correspond with the usual arrangement of the horny scutes of turtles. In 

 the specimen described by the writer in the American Naturalist (xxxn, 1898, p. 936) and in 

 the specimen here described on page 164,3 sulcus passes behind each of the tubercles surmount- 

 ing the neurals. This sulcus in each case separates two of the 

 vertebral scutes. Now, almost without exception, the first sulcus 

 crosses the first neural, the second crosses the third neural, the 

 third traverses the fifth neural. The position of the fourth trans- 

 verse sulcus varies somewhat, but it is usually found on the eighth 

 neural. In the present specimen the sulci must have crost on the 

 first, the fourth, the sixth neurals and the first suprapygal. It 

 seems evident that it is the third neural of the series that is an 

 intruder and disturber. In a specimen of Colpochelys kempt, in 

 the American Museum of Natural History, there are all together 

 13 neurals. The sulci cross on the first, the fourth, the eighth, 

 and the twelfth neurals. 



The nuchal bone has a width of 120 mm. along the free 



