360 



province not yet known to us." The Goniatites of this 

 fauna are associated with the niilhons of planktonic Styho- 

 lina, with floated logs, and probably other pehigic organisms, 

 and the sediment in which they were embedded was such as 

 probably AA^as not conducive to the well-being of such 

 animals, so that their occurrence is best explained by the 

 hypothesis of flotation. 



Of the embryology of Nautilus, and hence the whole group 

 of Tetrabranchiata, nothing is known. The Dibranchiata 

 develop directly Avithin the egg capsule, no veliger stage 

 occurring. 



Cirripedia. — The cirripeds, or barnacles, are marine seden- 

 tary benthonic Crustacea AA'hich have degenerated much from 

 the true type of crustacean, owing no doubt to their at- 

 tached mode of life. The body is covered with calcareous 

 plates A'ariously arranged, which fall apart after the death 

 of the animal, after which, from single pieces, it becomes 

 quite impossible to determine the species, owing to the 

 great variation of the skeletal parts (Darwin ). Balanus and 

 its congeners are sessile, being attached to the rocks and 

 other solid supports along the shore, seldom A^enturing into 

 water of great depths. Some species areexposed periodically 

 at low tide for many hours at a time, some, in fact, being 

 never covered more than one or two hours at flood tide, so 

 high up on the shore do they attach themselves. Balanus 

 has been found at a depth of 500 fathoms, but it usually 

 lives in lesser depths. Balanus improvisus occurs also in 

 brackish water. Coroimhi diadcma leads a pseudo-nektonic 

 life, attaching itself to the body of whales. Verruca incerta, 

 a common West Indian type, occurs in the Globigerina ooze. 

 Lepas and its congeners are pedunculate, attaching them- 

 seH'es by a fleshy peduncle, which represents the elongated 

 head end. Tlie majority of the Lepadida? are pelagic, lead- 

 ing a pseudo-planktonic existence, attached to floating logs, 

 pumice, or other objects. Three species of Lepas were found 

 by the ''Challenger" attached to theSargassam. Somemem- 

 bers of this family descend into deep water, Scalpellum 



