[9] THE BOTTOM OF THE GULF STREAM. 1053 



tbat abound on these bottoms. Manj' fishes, like the "hake" {Phycis), 

 of which two species are common here, have the habit of rooting in the 

 mnd like pigs for their food, which consists largely of Annelida and 

 other mnd-dwelling creatures. Other fisshes, those with sharp tails 

 especially, burrow actively into the mud or sand, tail first, and in all 

 probability Macrurus, abundant in this region, has this habit. Several 

 species of eels and eeldike fishes arc \ ery abund.tnt on these bottoms. 

 These are all burrowers. The "slim:^-eel" or hag {Myxine glufinosa) 

 was also taken in large numbers both in the trawl and in traps. Many 

 crabs and allied forms are active burrowers. Such creatures, by stir- 

 ring up the bottom sediments continually, would give the currents 

 a chance to carry away the finer and lighter materials, leaving the 

 coarser behind. 



In many localities in the region under consideration there are great 

 quantities of dead shells, both broken and entire. A small i)roi)ortiou 

 of the bivalves have been drilled by carnivorous gastropods, but there 

 are large numbers that show no injury whatever. There is no doubt 

 in my mind but that these have for the most part served as food for the 

 starfishes and large Actiniae, so abundant on these grounds, and from 

 which I have often taken entire shells of many kinds, including ptero- 

 l)ods. Many fishes, like the cod, haddock, hake, etc., have the habit of 

 swallowing shells entire, and after digesting the contents, they disgorge 

 the uninjured shells, and such fishes abound here. 



The raollusks represented by the numerous brokenshells have probably 

 been preyed upon by the crabs and other Crustacea, having claws strong 

 enough to crack the shells. The large species of Cancer and Geryon, and 

 the larger Paguroids, abundant in tbis region, have strength sutficient 

 to break most of the bivalve shells. Although I have often seen such 

 Crustacea break open bivalves for food, I am well aware that they also 

 feed on other things.* Many fishes that feed on mollusca break the 

 shells before swallowing them, so that both fishes and crabs have doubt- 

 less helped to accumulate the broken shells that are very often scat- 

 tered abundantly over the bottom, both in deep and in shallow water. 

 Such accumulations of shells would soon become far more extensive if 

 they were not attacked by boring sponges and annelids. Certain com- 

 mon sponges belonging to the genus Cliona very rapidly perforate the 

 hardest shells in every direction, making irregular galleries, and finally 

 utterly destroy them. In our shallower waters the most destructive 

 S|>ecies is G. sulphurea (Desor), which burrows in shells and limestone 



*I have observed that when in aquaria, many different species of the larger Crus- 

 tacea, siTch as the crabs, Libinia emarr/inaia, Cancer irroratus, Panopeiis Sayi, Carcinas 

 mcenas, Plattjonxcua occellatns ; the hermit-crabs, Eiipagiirus pollicaris, E. longicarpus, and 

 Catapagurus sociaViH ; the shrimp, Palwmonetes vulgaris and Virbius zostericola ; and iimu- 

 Im polyphemus, are all extravagantly fond of the masses of diatoms and other fine algse, 

 intermingled with copeopods, etc., which wo often collect in our surface-nets. When 

 a mass of such materials is thrown into an aquarium containing these Crustacea they 

 seize and devour it with great avidity. 



