88 H. H. NEWMAN. 



indicate that the extra scute is crowded to left or right. The 

 same letters indicate the side on which extra costals and mar- 

 ginals occur. 



The following isolated abnormalities have come to hand and 

 may be listed : 



Large specimen of Terrapene Carolina has a R 10 costal 

 (medium). 



Medium-sized shell of Cyclcmys doitata has paired 6 costals 

 (medium). See Fig. 42. 



Two medium-sized specimens of Chelydra scrpcntina have L 

 10 costal (large). 



Large AronwcJielys odorata has R 10 costal (medium). 



A reference to the literature enables me to list a considerable 

 number of similiar abnormalities. The names used in the refer- 

 ences will be retained. 



1. Ptychemys clcgans, Agassiz, L., Contributions to the Nat- 

 ural History of the U. S., Plate I, Fig. 13, showing: L 4 neu- 

 ral, paired 4 costals, paired extra marginals. (Figured in this 

 paper as Fig. 33.) 



2. Chelopas insailptns, Parker, G. H., paired marginals lacking. 



3. Same : R 8 and 10 neurals, R 10 costal, R marginals lacking. 



IN CATALOG OF SHIELD REPTILES IN THE BRITISH MUSEUM. 



4. Emysvermiculata^zb. XIII.), 24 neural, R 8 and 10 neural. 



5. Emys singuinulenta (Tab. XV.), R 6 neural, R 6 costal, L 

 4, 6 and 10 costals. 



6. .Cyclcmys dentata (Tab. XIX.), median 4 neural, R 6 neural, 

 L 8 neural. 



7. Chclodina oblonga (Tab. XXIV.), R 8 neural. 



IN HISTORIA TESTUDINUM, SCHOEPFF, J. B., 1792. 



8. Testudo cincra (Tab. III.), Fig. 2, paired I costals. 



9. Tcstndo arcolata (Thunberg), Tab. XXIII., median 8 neural, 

 L 6 costal. 



10. Tcstndo planiccps, XXVII. , L 4 costal. 



Discussion. 



A scute, whether normal or supernumerary, is a separate and 

 definite entity, resulting from a definite embryonic primordium. 



