as the little Stylifer, which lives on the spines of sea urchins and star- 

 fishes. A whole order, the Nudibranckiata, or sea slugs, are destitute 

 of a shell, although possessing calcareous spicules, or spines in the 



skin, which serve to make the body rigid. The 

 breathing organs, or branchiae, are placed on the 

 outside of the animal, near the posterior part 

 of the body, and look like leaves. The animals 

 are also brilliantly colored. Another order, the 

 Pt&ropoda, is composed of mollusks called sea butter- 

 flies, on account of the two swimming lobes, which 

 are incessantly moving. The shells are of various 

 shapes and sizes, glassy, thin, and transparent. 

 These animals are pelagic ; that is, live always in 

 the ocean, and never approach land unless driven 

 in by a storm. They feed on microscopic animals, 

 and are in turn eaten by whales and fishes." 



After spending some little time examining his 

 new collection of marine shells, we bade the Pro- 

 fessor good by, he promising in the near future 

 to allow us to accompany him on a collecting trip. 



Hyaltea trispinosa, 

 a common sea butterfly, 

 or pteropod. Note the 

 two swimming lobes, or 

 "wings,' 1 from which the 

 order receives its name. 

 (Tryon.) 



a 



A poor collecting locality. 

 124 



