342 mi8C]:llaneous tapers. 



of Fierafifer are well known, and Putnam describes, in the ' Proceedings 

 of tbe Boston Society of Natural History,' Vol. xvi, 1874, p. 34:4, a spe- 

 cies, Fierafifcr dubius, which is found on both coasts of Central America, 

 but inhabits holothurians on the Atlantic and pearl oysters on the Pa- 

 cific side; and he further mentions, in a foot-note, an example belonging 

 to the Museum of Comparative Zoology at Cambridge, in which also a 

 Fierasfer has been imbedded in the substance of the shell. In this case, 

 as well as in ours, the fish, instead of introducing itself into the cavity 

 between the two halves of the mantle, penetrated between the mantle 

 and the shell, causing irritation to the mollusk, which the latter resented 

 by immediately secreting the substance with which the intruder is iu:)w 

 covered. It is remarkable to note that the secretion must have taken 

 place in a very short time, at any rate before the fish could be destroyed 

 by decomi)Osition." 



Soon after the close of the New Orleans Exposition Prof. P. Perrari 

 Perez and Senor J. G. Aguiiera, of the Mexican Geographical Commis- 

 sion, visited Washington and remained here for several weeks for the 

 purpose of comparing and identifying various natural history material 

 with the assistance of the curators in different departments of the Na- 

 tional Museum. 



The collections in charge of these gentlemen, so fiir as molluscan fornig 

 are considered, were rather meager, though many interesting points 

 l)ertaining to geographical distribution were derived from the examina- 

 tion. 



The collection included a hundred or more valves of the common pearl 

 oyster of the Pacific coast of Mexico, Mclcagrina fimhriaia Dkr., of 

 which two or three species have been made by as many authors. Upon 

 examining these last winter I found a single valve (see Plate II, Fig. C), 

 the right half of a rather young individual in which was imbedded, in 

 very nearly the same region as in the specimen mentioned b^' Dr. Ciin- 

 ther, a small fish of rather a long and slender form, probably of the 

 same genus and perhaps the same species as that inclosed in his (Giin- 

 ther's) pearl-oyster valve, and previously described by Putnam, as 

 quoted by Giiuther. The Mexican collection contained but a single 

 specimen of this special character. 



ANOTHER SPECIES OF FISH DETECTED. 



Among the lot, however, were two or three valves, in each of which, 

 inclosed in nacreous splendor, was a specimen of a small fish, apparently 

 a species of OJifjocottus* In each instance the fish had worked its way 

 between the interior face or surface of the valve and the mantle towards 

 and near to the adductor muscle, as can be seen by examining the shell 

 close by the muscular scar. 



The squarish, chunky head of the little intruder, also the somewhat 



* Submitted to Dr. Bean, curator of ichthyology, who, though not ]) 

 fieilly refers it to this group. 



