1871.] 143 [Morse. 



In a general -way we recall the sombre colors of the shells of most 

 species, varying through different shades of yellow, brown and green, 

 in this respect resembling the sand, mud and rocks, or sea weed in or 

 upon which they live, and we then recall by groups the land snails of 

 our woods with their almost uniform brown tints, like the dead 

 leaves or rotten wood in which they live. 



The fresh water snails have similar shades to match their peculiar 

 habitats. 



The fresh water mussels, colored likewise brown, greenish or black, 

 accord with their places of refuge. 



Among the marine forms we notice the adaptive coloration of cer- 

 tain species very well marked. The common Littorina of the coast 

 swarms on the bladder weed, the bulbous portions of which are olive 

 brown in color, or yellowish according to age. The shells of the 

 Littorina found upon it, present in their varieties these two colors 

 and are limited to these colors, though now and then delicately 

 banded specimens are seen. 



Purpura lapillus, which generally hides beneath overhanging ledges, 

 or is concealed under flat rocks, has generally a dirty white shell, with 

 now and then a specimen bright yellow, or banded with brown. We 

 are not aware of any fish that feeds upon this species, though in 

 the almost universal white color of the species an adaptive color may 

 be secured in resembling the white barnacles which oftentimes 

 whiten the rocks by their numbers. 



In pools left at low tide where the rocks are often clothed with the 

 red calcareous algse we find the little red Chiton. Certain Mytili are 

 green. The young of the large M. modiolus has a rough coat of 

 epidermal filaments looking like the aborescent growth of some Algse 

 or Hydroid. 



The few species common to the mud flats exposed by the retreat- 

 ing tide are colored black or dark olive. Ilyanassa obsoleta has the 

 shell black, while the soft parts are quite dark. A related form, 

 Nassa trivittata, lives in more sandy places and has a similarly colored 

 shell. Rissoa minuta, inhabiting mud flats, has a shell dark olive, or 

 nearly black, while other species of Rissoa are much lighter in color. 

 The fronds of the large Laminarian are frequented by Lacuna vincta 

 and its variety fusca. The first is greenish or purplish horn color, 

 with darker bands, while the variety fusca is uniformly dark brown 

 or chestnut; the colors in both cases quite match the Laminarian 

 upon which they are found. Another species of the same genus, 



