Diversity in the Scutes of Chelonia. 65 



comparatively broad ou both sides but widest on the side where they 

 are in proper alternation with the costals. The subject has been so 

 fully discussed in a previous section that I need only refer to the 

 figures : Figs. 61, 62, 6-i, 72, 70, 84, 85, 90, 91, 100, and a few others 

 that need special discussion. 



In No. 80 (Fig. 78) there is the normal number of neurals with, 

 evidently, a pair of supernumerary costals ; N4 is a large scute 

 where we would expect two scutes to complete the alternation ; but 

 we find on each side the beginning of division opposite the apices of 

 costals. 



In IsTo. 210 (Fig. lO-lJ the incomplete seam on the left side is to 

 be noted. 



In 73 (Fig. 81) the correlation is complete except in so far as two 

 of the seams are incomplete mesially. 



'No. 78 (Fig. 82) presents an unexpected scute in the oblique 

 fourth neural. The incompleteness, mesially, of its anterior seam 

 suggests that this scute was still more abnormal at an earlier stage. 

 But if this carapace is to be in harmony with the others, we would 

 expect the development of a seam from the point x extending toward 

 the left end of the third neural or toward the second costal.* 



E"o. 94 (Fig. 90) has already been referred to; but it is to be 

 noted that two of the seams are completed in the mesial region only 

 by furrows. 



No. 92 presents a clear case of "mal-adjustment" (Fig. 87). N2 

 is an exceptionally large scute and there are not even the beginnings 

 of seams from the apices of the third costals. It is not surprising, 

 however, that this turtle should fail to manifest the usual laws of 

 development in scutes or in any other organs. Its "cyclopean defect" 

 alone gives it a hopeless deformity. 



"Incomplete Division." 



It may be said that it is "begging the question" to assume that 

 the incomplete seams represent division rather than fusion. Against 

 the latter explanation it may be said that such seams are always 

 in the peripheral or growing region of the scutes, and that, where 



*The letter is omitted in tlie plate. The poiut x is on the fourth neural seam 

 near the apex of the third right costal. 



