596 HISTORY AND METHODS OF THE FISHERIES. 



and much warmer than on the coast of Maine, this species again occurs in some abundance, asso- 

 ciated with the oyster and many other southern species that are also absent from the northern 

 coasts of New England, and constitute here a genuine southern colony, surrounded on all sides, 

 both north and south, by the boreal fauna. 



Concerning the curious instance of a colony isolated in Casco Bay, Maine, Prof. A. E. Verrill 

 draws some quotable inferences in a late Report of the U. S. Fish Commission. From a critical 

 examination of this and similar colonies, Prof. A. E. Verrill concludes : 



"First, that in the Post-pliocene and Cham plain periods the coast was at a lower level, and 

 the marine climate of Casco Bay colder than at present, probably that of the present Newfoundland 

 or Labrador coast. Second, that at a subsequent period, when the coast had attained nearly or 

 quite its present level, the marine temperature was considerably higher than at present. Third, 

 that the temperature of these waters has gradually declined, but was still somewhat higher at the 

 period when the Indian shell heaps were formed than at present." 



A like conclusion is reached by the examination of a somewhat similar colony on the Saint 

 Lawrence. Professor Verrill ascribes the survival of these earliest colonies to the fact that, in the 

 increasing coldness of the water, the peculiar isolation and other favorable conditions of their 

 position protected them against the general fate of their neighbors. 



This clam is thus assigned to a very ancient race. 



The home of the quahaug everywhere is on sandy and muddy flats, just beyond low-water 

 mark. It also inhabits the estuaries, where it most abounds, especially in shallow but pretty 

 salt water. It is also found on oyster beds, when these do not take the form of rocky reefs, and 

 in this capacity often helps the unconscientious to defy the laws, by alleging, whenever they are 

 caught tonging or raking on forbidden ground, that they are only getting clams and would be 

 glad of all the assistance the discoverer might give in culling out oysters accidentally caught. On 

 these bottoms of sand and mud the clam spends most of its time in crawling about with the shell 

 upright and partly exposed. It can travel pretty fast, and leaves behind it a well plowed fur- 

 row. Sometimes it is left bare by low spring tides when making these excursions. In such cases, 

 if it wishes, or at any other time, it can easily and quickly burrow beneath the sand by means of 

 its thin-edged but broad and muscular foot. The lobes of the mantle are separate all around the 

 front and ventral rim of the shell, and their edges are thin, white, and folded into delicate frills. 

 Owing to this broad opening in the mantle, the foot can be protruded from any part ot the ventral 

 side, and has an extensive sweep, forward and backward. The foot and mantle edges are white; 

 but the two short siphon-tubes for, not burrowing far down like the soft clam, it has no need of the 

 long distensible feeding apparatus of that and the razor-fish are united from their base to near 

 the ends, and are yellowish or brownish orange toward the end, more or less mottled and streaked 

 with dark brown, and sometimes with opaque white. When very aged, so as to deserve the New 

 Jersey term "bull-nose," the whole flesh loses its white color and becomes a dirty, forbidding 

 yellow-brown. 



The generation of the quahaug is after the general plan of Lamellibranchiate mollusks, but I 

 am not aware that any naturalist has made its embryology a special study. The eggs are prob- 

 ably fertilized within the body, and sustained in the folds of the mantle and gills until they have 

 attained rudimentary shells, when they are sent out and lie upon the bottom to become the food 

 of crabs, ground-feeding fishes and various other enemies to their welfare. This happens early in 

 summer, and the young are sometimes observable in enormous numbers. In the summer of 1879 

 the shallow sand-beach opposite Babylon, Long Island, for 10 miles in length was crowded with 

 young quahaugs from the size of a pin-head to that of a silver 3-ceiit piece. The succeeding 



