18 PROCEEDINGS OF THE ACADEMY OF 



mostlj^ naked, reminding one of the texture of a bat's wing. 

 In color, they are like the tail ; usuall}^ dark, blotched or rimmed 

 "with flesh-color ; but they may be wholly blackish or mostly 

 whitish ; it is impossible to base any character upon their colora- 

 tion. The general shape of the conch may be called pyriform 

 (base uppermost) or subcircular ; but it is not easy to see what 

 the shape really is, unless the ear is pressed out flat. From their 

 texture, they shrink and shrivel in drying. I have never seen a 

 Virginian opossum with so pointed an ear as " D. californicus" is 

 represented to possess in pi. iii. of the Mexican Boundary Sur- 

 vey ; but if, as I presume, the drawing was made from a dried 

 specimen, it is not trustworthy in this point, for indeed the true 

 shape of the ear could have been only guessed at. The ears, like 

 the tail, are peculiarlj^ subject to disease ; and may ulcerate aAvay 

 entirely, as I have observed in animals kept in confinement ; and 

 this, too, without appreciable general ill-health. 



The general body colors are amongst the most variable features. 

 The variation is largely a matter of individual diflerence; but 

 there are certain things that influence it in a general way ; espe- 

 cially age. The opossum grows gray with age, as a rule ; half- 

 grown ones seen at a little distance give the impression of a 

 blackish animal; old ones, of a whitish animal. The paws are 

 particularly variable. Generally, they are among the darkest 

 parts, and are often quite blackish ; frequentl}' , they are as pale 

 as any other parts. Not to go into tedious particulars in this 

 connection, I may say, in short, that I have seen no points of 

 coloration adduced for D. californica that might not be easily 

 matched out of a dozen individuals of the Eastern species, with 

 a single exception. To the best of my recollection, I have not 

 seen a specimen of Virginiana with paws completely black to the 

 nails. 



Under the circumstances, it seems most probable that a second 

 species of Didelphys remains to be determined, if occurring 

 within our limits. 



II. BIEDS. 



The list is restricted to those species that came under personal 

 observation on the unwooded portion of the island itself, and on 

 the waters of the immediate vicinity ; for an exhibit of the strictly 

 littoral and maritime bird fauna, as distinguislied from that of 



[May 2, 



