1889.] NATURAL SCIENCES OF PHILADELPHIA. 345 



irregular brownish bands, closely resembling the branched fronds of 

 the Sargassum weed. Along the edges of these darker bands, on the 

 bands themselves, and also to a lesser extent upon the rest of the body, 

 are little white specks of various sizes, on an average about that 

 of a pin's head. On the belly, around the mouth, and on the 

 dorsal spines, are numerous leaf like cutaneous filaments. Mr. Ives 

 stated that after careful consideration, he had come to the conclusion 

 that the color markings of the fish, and the cutaneous filaments, had 

 been developed in mimicry of the Spirorbis-covered Sargassum weed. 

 Professor Benjamin Sharp who spent last winter in the West Indies, 

 had informed Mr. Ives that on the Sargassum weed, of which he saw- 

 large quantities, were invariably scattered great numbers of Spirorbis 

 .shells. Professor Moseley in " Notes by a Naturalist on the ' Chal- 

 lenger'" (p. 567) speaks of the resemblance in coloration of the 

 forms inhabiting the Sargasso Sea, to the Sargassum weed. He 

 attributes the white spots of Pterophryne histrio, and also of some 

 shrimps and crabs to mimicry of the patches of Membranipora that 

 encrust the Sargassum weed. The white spots upon Pterophryne 

 histrio. however, are much smaller than the patches of Membranipora, 

 and are also much more striking to the eye. This latter fact appears 

 to be due to the delicate fenestrated character of this Bryozoan. The 

 patches of Membranipora, also do not occur in the same abundance 

 upon the Sargassum weed as do the Spirorbis shells. Professor 

 Moseley probably confounded the numerous Spirorbis shells with 

 patches of Membranipora. As far back as 1757, Peter Osbeck 

 describing this fish which he had met with in the Sargassum weed 

 of the Atlantic Ocean while on a journey to the East Indies, said, 

 with reference to the cutaneous filaments, " probably Providence has 

 clothed it in this leaf-like manner, in order that the predaceous fishes 

 might confound it with the sea-weed, and therefore not exter- 

 minate it." 1 *, 



November 12. 



Mr. Charles P. Perot in the chair. 

 Twenty-eight persons present. 



Xotes on Orepidula. — Mr. John Ford exhibited fine suites of 

 Crepidnbi, including C. convexa, Say, C. plana, Say, C. fomicata, 

 Linn, and C glauea, Say, with the view of proving that C. glauca, 

 said by some writers to be the young of C. fomicata, is not only 

 distinct from that species but from all others of the genus. 



Special reference to the matter had been suggested by the omis- 

 sion of the name in Dr. Dall's recently published "Catalogue of the 

 Shell-bearing Marine Mollusks of the South Eastern Coast of the 



1 Peter Osbeck, Rei>e nach Ostindien und China. Aus ilem schwedischen 

 iibersetzt von J. G. Georgi Rostock, 17b'5. p. 4011. 



