MUSEUM OF COMPARATIVE ZOOLOGY. 139 



Dr. Elliott Coues ("Osteology and Myology of the Opossum," Me- 

 moirs of the Boston Nat. Hist. Soc, II. 62) treats of the cthmotur- 

 binal as synonymous with the lateral mass, and of the perpendicular 

 plate as being probably homologous with a pair of coalesced prefron- 

 tals. He further ambiguously states that the "spongy convolutions" 

 are borne on either side of the perpendicular plate. Respecting the 

 arrangement of the olfactory plates, he remarks, " It would be diffi- 

 cult even if it were desirable (!) to describe the details of the spongy 

 convolutions." 



The description in Bronn's Klassen und Ordnungen des Thier-Reichs 

 (Bd. VI. Abtheil. X. 52) embraces a general account of the bone. 

 No attempt is made to discriminate between the olfactory plates. The 

 ethmoturbinal mass is named the labyrinth, and composed of thiu rolled 

 plates of bone enclosing the. ethmoidal cells. 



The Method employed by the Author in studying the Ethmoid Bone. — 

 The study of the ethmoid bone is greatly facilitated by immersion of 

 the bone in an acid solution which is sufficiently strong to remove 

 the bone-salts. . When the bone is detached from the skull, the deli- 

 cate folds are easily decalcified by a solution of nitro-muriatic acid of 

 not greater strength than eight drops of the acid to an ounce of 

 water. When the entire skull, say of an animal of the size of a horse 

 or dog, is subjected to the acid solution, a strength from a half-drachm 

 to a drachm of acid to the pint of water will be required. For small, 

 delicate skulls, such as those of the bats, a fluid slightly acidulated, 

 say two drops to the ounce of water, is sufficient. Immersion from 

 six to twelve hours is needed for the smaller specimens, and perhaps 

 a renewal of the fluid for a second period as long as the first for the 

 larger ones. The specimen is next washed and soaked through sev- 

 eral waters, and afterwards can be preserved in alcohol. The ethmoid 

 bone thus prepared can be studied with signal advantage over the 

 natural bone, since a dissection can be effected with ease, and without 

 danger of mutilation. I think perhaps the best way to obtain a satis- 

 factory preparation for general purposes of comparison is to secure a 

 macerated skull * of the animal whose ethmoid is desired, and, after the 

 bone-salts have been removed, to bisect the skull longitudinally at one 

 side of the line of the vomer, and reserve one half of the specimen 

 for study of the median surface of the ethmoid bone. The encranial 



* Care must be taken to protect the freshly macerated skull from tlie attacks of a 

 voracious dipterous larva, that is capable of destroying the delicate structures of the 

 ethmoid in an incredibly short space of time. 



