ORTHOGEXETIC VARIATION IX THE SHELLS OF CHELONIA. 



209 



£ 



12 



13 



14 



15a 

 166 



16 



17" 



175 



18a 



186 

 19 • 



196 



Size 



New born 

 New born 



New born 



New burn 

 New born 

 New born 



New born 



New born 

 8 inches 



8 inches 

 New born 



13 inches 



Locality 



B. M. Manado 



B. M. Batavia. 

 Bleeker Collect. 



Willey, 5 



Wili--- . 6 



Leiden Museum 



B M. Indian 

 Seas. Theobald 



B. M. Indian 

 Seas. Theobald 



Manchester Mus. 

 B. M. Muscat 



Amsterdam 



B. M. Little 

 Cayman. Lievit. 

 Carpenter Coll. 



Amsterdam 



Observations 



5th neural very small, 

 much reduced. 



4th right and left costals 



6th neural very small. This would be very ex- 

 ceptional, but the same scute is also the last 

 but one, and this coupled with the small size 

 of the right and left 4th costals, while the 5th 

 neural is large (and not small as is usual in 

 such cases) suggests that in this specimen the 

 original 5th neural has already fallen out. 



There are 14 marginals on the left side and 

 the lateral corner is formed by the 6th. This 

 supernumerary condition is caused by the two 

 first marginals being very small and not yet 

 being fused into one larger scute as on the 

 right side, which is normal. Cf. specimen No. 

 L8a. 



7th left costal small. 



5th neural and 4th left costal small. 



5th neural and 4th left costal small. 



Last but one neural and 6th right costal very 

 small. There are apparently only 7 neurals, 

 but the first neural is very large and shows by 

 its composite shape that it lias been produced 

 by fusion of two successive neurals; cf. speci- 

 men No. 24. ('(Hinting this large neural scute 

 as 1 4- 2, the last but one would be the 7th as 

 in specimens 1, 2, 3, 7. 



(Added during correction of proof.) 



2nd neural extremely small and asymmetrical. 

 ,13 right and 14 left marginals, and the 6th left 

 forms the lateral corner as in specimen No. 

 14. 



5th neural small. 12 right and 13 left marginals. 



None of the neurals are reduced. The specimen 

 is quite symmetrical. There are only 12 mar- 

 ginals on either side, and the lateral corner is 

 formed by the 4th marginals. 



6th (last but one) neural very small, the 1st 

 left costal very small, the corresponding right 

 scute being absent. See remarks on stage 

 VII. p. 218. 



30- 



1 1 



12 



13 



14 



15 



16 



2li 



