I 



1886.] NATURAL SCIENCES OF PHILADELPHIA. 211 



agree with the corresponding teeth of Toxodon Burmeisteri^ 

 described and figured by Dr. Burmeister, in the Annals of the 

 Museum of Buenos Aires, 1869, 256, pi. xi. 



The molar tooth is the penultimate of the left side. Its length, 



when complete, has approxi- 

 mated five inches, and it mea- 

 sures 43 mm. fore and aft, and 

 18 mm. transversely at its fore 

 part. An outline of the tritu- 

 rating surface is represented in 

 figure 2. Enamel invests the 

 outer surface extending about half way round the corners in front 

 and behind. On the inner surface enamel invests the middle 

 extending furthest behind. The inner angles of the tooth are 

 both destitute of enamel. The outer enamel layer forms a single 

 inflection about the anterior third of the tooth ; the inner enamel 

 layer forms two inflections nearly equidistant behind the position 

 of the outer one ; the posterior inflection being the deepest. 



The incisor, apparently the second lower of the right side, is 

 broken into two about the middle, and when complete has been 

 over six inches long. The transverse section, as seen in figure 3, 



viewed from below, is triangular, with 

 the apex directed outward, and the 

 base inward or mesially. The front 

 surface is transversely convex, and 

 the back surface in the same direction 

 concave. The inner surface, extending 

 around the corners, further in front 

 than behind, is destitute of enamel. 

 The triturating surface is worn away in a slope from the outer 

 border inward and backward. The measurement of the section 

 in front and behind is 37 mm., and internally fore and aft 23 mm. 



June 8. 

 The President, Dr. Leidy, in the chair. 



Twenty-one persons present. 



A paper entitled " On the Histology of Salpa (S. runcinata- 

 fusiformis)," by Dr. Chas. S, Dolley, was presented for publi- 

 cation. 



Oa the Expansion of the Crystalline lens. Dr. Benjamin Sharp 

 remarked that it is well known that accommodation in the eye, 

 for distance, is effected by the contraction of the ciliary muscle, 

 drawing on the point of attachment of the capsular ligament of 

 the lens, the lens widening its optical axis as soon as the tension 



