DALL: MOLLUSCA AND BRAOHIOPODA. 201 
Cavolina telemus A. Adams, Ann. Mag. N. Hist., 1859, 3d ser., 3, p. 44. 
Cavolinia tridentata Fischer, Man. de Conchyl., 1888, p. 434; Pelseneer, Chall. Rep. 
Pter., 1887, p. 83. 
Station 3407, U. S. S. “ Albatross,” in 885 fathoms, near the Galapagos Islands. 
This species was obtained by the “ Albatross " in 1887 at several stations in the 
South Atlantic off the coast of South America and is widely distributed in the 
open sea of both the Atlantic and Pacific oceans. A long list of stations is given 
by Boas, and Arthur Adams reports it common in the Atlantic and Indian oceans. 
The tendency of the early authors who had small collections of pteropods was 
to name each distinguishable form, and doubtless far too many names were pro- 
posed. The reaction from this has swung the pendulum in the other direction 
perhaps too far, and it is probable that a more thorough knowledge of the living 
animals would show the truth to lie between these extremes. The uniformity of 
the living animals taken from a single swarm, and the wide differences of form, 
color, and proportion which appear in the sketches made from life, can hardly all 
be attributed to errors of the draughtsman, though the latter must also be allowed 
for. It is the writer's opinion that future investigation will show that there are 
some species of Cavolina, at least, which have very similar tests, but differ in form 
and color of the flippers and other parts of the body. 
The full illustration of the stages of growth in the various thecosomatous ptero- 
pods is yet a desideratum. 
The unequal contraction of muscular and cellular tissue in alcohol, which is 
exceptionally great among the pteropods, prevents the student of alcoholic mate- 
rial from gaining any just idea of the proportions of the living animal, while its 
rich violet or crimson coloration is almost wholly lost. 
Dr. J. I. Peck discussed the pteropods of the “ Albatross” voyage around the 
Horn, but the very few collected, and the small number of stations, render gen- 
eralizations on his material of very little weight. 
The rapid dissolution of the fragile pteropod shells under the influence of the 
carbon dioxide contained in sea water at considerable depths is absolutely cer- 
tain, and unless the dead shells were almost immediately recovered by the dredge, 
no trace would remain of them. It is probable that a very few months are all 
that is needed to completely dissolve the shell of a Cavolina or Cleodora. In 
regions where there is a considerable quantity of organic lime-material on the 
bottom, as off St. Augustine, Florida, in 400 fathoms, the small pteropod shells 
aceous areas they are found 
are well preserved, but in the deeper and more argill 
Henoe little can be safely 
with extreme rarity, though abundant on the surface. 3B 
predicated from the absence of pteropod shells on a given bottom, a nd it 18 abso- 
lutely unsafe to base generalizations of distribution upon negative evidence of this 
kind. 
The season of the year and the state of the 
with the abundance and even the presence of pteropods. In the Pacific the writer 
und the Aleutian Islands, 
great oceanic currents has much to do 
has made some twenty-six voyages between California ¢ 
on nearly all of which a tow net was kept going. Consequently a tolerably full 
