PEARL OYSTER PARASITES, ETC. 343 



prominent spines of the head, are easily discerned, though covered and 

 partially obscured by the coating of nacre. (See Plate HI, Fig. D.) 



The single specimen containing the inclosed Fierasfer was retained 

 by the commission, but one of the others (Plate III, Fig. E) was kindly 

 presented to the National Museum. (So. 73934a.) 



I am not aware that the occurrence of OUgocottus in this way has here- 

 tofore been observed or made known. 



This determination is not positive. The specimen (73931fl) repre- 

 sented in Plate III, Fig. E, is not as favorably presented for this pur- 

 l)Ose as in the others in the possession of the commission. 



The genus OUgocottus Girard includes certain small fishes inhabiting' 

 rock pools between tide marks on the Pacitic coast of North America. 

 The species described, and their distribution as given in Jordan and 

 Gilbert's Synopsis of the Fishes of North America (Bulletin of the U. 

 S. National IVIuseum, No. IG), is as follows : 



O. analis Grd., coast of California; abundant in rock pools, from 

 Monterey southward to Lower California. 



0. maculosus, Grd., San Luis Obispo to Alaska, exceedingly abun- 

 dant northward. 



0, glohiceps, Grd., Pacific coast northward to Kodiak, in rock pools ; 

 rather rare. 



Assuming that Dr. Bean is correct in jilacing the above in this group, 

 it will be observed that whether it belongs to the more southern species 

 of the three (0. analis) or otherwise, the geographical disribution is 

 evidently considerably extended, as the pearl oysters in which our 

 specimens are inclosed came from the Gulf of California, where the 

 fishery of these shells is carried on. 



After entering the shell, which of course must be at such time as 

 tlie valves are partially open or gaining, these fishes find no obstruction 

 to their course as they push their way towards the interior between the 

 mantle and the smooth inner surface of the valves until they approach 

 the adductor muscle, and here they find a barrier which most likely 

 causes them to expend somewhat greater activity or energy and conse- 

 quently in a correspondingly increased degree disturb the serenity if 

 not the structural economy of the oyster. 



Having reached thus far, the invader is in the immediate vicinity of — if 

 not the seat of intellect, then — the center of sensitiveness. The deposit 

 of nacre in such instances must be very rapid, and it is quite possible 

 that the unwelcome explorer is not only enshrouded and entombed in 

 pearl, but previously drowned in a pearlaceous flood, for it may be rea- 

 sonably presumed that the annoyance caused by its presence must be 

 exceedingly great, and likely to induce a copious flow of nacreous lymph 

 at the point and in the region of greatest irritation. 



It is evident that the deposition and induration are sufficientlv rapid 

 to inclose the parasite before decomposition has taken place. 



December 15, 188G. 



