Diversity in the Scutes of Chelonia. 27 



part is in contact with MIO, it may fairly be regarded as a terminal 

 costal that encroaches slightly on the neural region. 

 Compare : 



No. 195, PI. Ill, Fig. 8, medium scute, left side 



No. 199, PI. X, Fig. 43, medium scute, left side 



No. 21u, PI. jyJj'JFig. j jM medium scute, left side* 



aud, possibly, 

 No. 181, PI. X, Fig. 47, medium scute, left side 



No. 149, PI. IV, Fig. 11, large scute, left side 



3. A scute which overlaps the last marginal and is not in contact 

 with any marginal anterior to the next most posterior (Mil, in 

 typical marginal series), is within the neural region and must be 

 classed as a neural. 



Compare : 



No. 222, PI. X, Fig. 48. 

 No. 2.52, PI. XI, Fig. 49. 

 No. 256, PI. VII, Fig. 23, small scute ou right side. 



It is doubtful whether the extra scutes on the left in ISTos. 149 

 (PI. IV, Fig. 11) and 181 (PI. X, Fig. 47) should be included in 

 this or the preceding class. The small scute on the right in ISTo. 247 

 (PL VIII, Fig. 24) would seem to belong in the first class, but the 

 shape of the areolse of this and of 'N5 and its manner of growth as 

 indicated by the rings suggest clearly that it is but the separated 

 lateral end of ]Sr5. 



It may be that this scheme of classification, as applied to such 

 specimens as ISTo. 198 (PI. X, Fig. 45) and 256 (PI. VII, Fig. 23) 

 is quite arbitrary. This leads to the general question whether the 

 reference of many of the abnormal scutes to nonnal series has any 

 other merit than that of convenience of description. This question 

 will be referred to in a later section, but it is well to make clear the 

 difficulty of identification because, if abnormal scutes are to be 

 regarded as of morphological value, rational and exact classification 

 is essential. 



The difficulty of diagnosing the costal series of cases like Xo. 151 

 (Figs. 7 and 15, right side), 167 (PL VII, Fig. 16, left side) and 

 210 (Figs. 5 and 17, both sides) has been referred to. In Xo. 210, 



*Cf. footnote (*) preceding page. 



