NATURAL SCIENCES OP PHILADELPHIA. 73 



length of the body, which is about five lines. In ouc instance 1 saw a Im.w tl 

 Hydra from the Schuylkill, the body of which was live lines in length, eloti| 

 its arms to nearly three inches. The green Hydra is found nunc especiall 

 the under side of floating: leaves in quiet ponds. It usually has five ai 

 though I have observed six, and more rarely seven ; and this is also the case 

 with the brown Hydra, which sometimes has but four arms. As in 11. viridis, 

 the arms of our green Hydra are shorter than the body. 



July V2th. 



The President, Dr. PiUSCHenberger, in the Chair. 



Ten members present. 



Poof. Leidy exhibited a fossil, submitted to his examination by the Smith- 

 sonian Institution. It consisted of a much mutilated portion of a ramus of 

 the lower jaw of a large ruminant. The specimen, very friable and encrusted, 

 was found 22 feet below the surface, in clay, on the " bench " or " second 

 bottom " of Boyer River, Harrison Co., Iowa, and was presented to the Smiths. 

 Inst, by D. R. Witter, of Woodbine, Iowa. Other bones were discovered in 

 association with the specimen, but crumbled to pieces. 



The jaw fragment was especially interesting, as it is supposed to belong to 

 Ooibos cavifrons, and is the first specimen of a lower jaw yet discovered which 

 may be attributed to that animal. It contains the last molar tooth nearly < n- 

 tire, but much worn. This tooth is constructed after the type of the corres- 

 ponding one in the Sheep, and exhibits no trace of the accessory fold between 

 the anterior and median pairs of lobes such as exists in the Ox, nor of a tuber- 

 cle such as is found in the same position in the Deer. The fore and aft 

 measurement of the crown of the tooth is full two inches; the width at the 

 fore part of the crown is nearly an inch. 



An isolated tooth, a last lower molar which had not yet protruded from the 

 jaw, from Natchez, Mississippi, preserved in the Museum of the Academy, by 

 comparison with the tooth in the jaw fragment, would appear to belong to the 

 same animal. The specimen is two and a quarter inches long and three- 

 fourths of an inch wide at the fore part, and is two inches in its anteropos- 

 terior measurement. 



Mr. T. Hale Streets made the following remarks on the cranium of an 

 owl : 



Among the Academy's collection of birds' crania there is one belonging to 

 a species of owl (supposed to be the Nyctale acadica), which presents a very 

 remarkable instance of the want of symmetry in corresponding parts of oppo- 

 site sides. 



In this skull the squamous portion of the temporal bone is thin and scroll- 

 like, and joins the post-frontal plate. What is interesting about it is the man- 

 ner in which this union takes place. On the right side the lower end of the 

 scroll-like squamous bone turns upward and forward, and unites with the 

 post-frontal. On the left side the contrary to this is the case; the upper ex- 

 tremity of the bone curls over and joins the post-frontal, while the lower ex- 

 tremity is free. 



If there had been but a single specimen of this cranium I would have been 

 led to regard this instance of symmetry as abnormal ; but as the same pecu- 

 liarity of structure is presented by two (these being the only representatives 

 of the species in the collection), it would rather suggest itself as a normal 

 condition, although instances of coincidence of abnormality exist, especially 

 in the lower forms of life. 



July im. 



The President, Dr. Ruschenberger, in the Chair. 

 Fourteen members present. 

 1870.] 



