158 REPTILIA (the turtle) 



(2) The Posterior Limbs. 



(a) Number of digits? 



(b) Are they webbed or free? 



(c) Use? 



(3) Compare the anterior with the posterior Hmbs. 



(a) In what respects are they ahke? 



(b) In what respects do they differ? 



(c) Give reasons for these resemblances and differ- 



ences. 



6. The Skin. 



(1) Smooth or rough? 



(2) Thick or thin? 



(3) Where thickest? Where thinnest? AVhy? 



(4) Loose, hke the frog's skin, or tight? 



(5) Color? " 



7. The Shell. The upper portion is the carapace, the lower 

 portion is the plastron. 



(1) The Carapace. 



(a) Sketch it — one-half natural size. 



(b) How many marginal epidermal plates? Letter 



each of these in your sketch (a). 



(c) How many dorsal plates? Letter each (b). 



(d) How many costal plates (between marginal and dor- 



sal)? Letter (c). 



(e) Now write a brief description of these epidermal 



plates, stating the total number, and the shape, 

 size, color, use, and arrangement of the different 

 kinds. 



(2) The Plastron. 



(a) Sketch it. 



(b) Of how many epidermal plates is it composed? 



(c) What is their size, shape, color, and arrangement? 



(d) Compare plastron with carapace as to shape, size, 



and relation to other parts. 



B. Internal Morphology 

 1. Preliminary Work. 



(1) Killing the turtle. Take a firm hold of its head and 

 open its mouth. Insert a blow-pipe into the glottis 



