Mighels'' Descriptions of Six Species of Shells. 345 



they have, probably, been transported by the Gulf Stream. If 

 this is true, although it does not prove, it certainly adds some 

 strength to the supposition, that the species of shells above 

 alluded to have been transported across Massachusetts Bay by 

 a current not hitherto observed, from some region south of 

 Cape Cod. 



I would by no means be understood as recording this as 

 my settled opinion, I merely throw out these hints in the hope 

 of eliciting the opinions of others. 



Since writing the above I have had an interview with Capt. 

 Walden, who confirms my conjecture. He says there are two 

 periodical currents, — one sets eastwardly around Cape Cod, 

 and extends into the Bay of Fundy ; it frequently flows at the 

 rate of two miles an hour, and continues for several weeks in 

 succession. The westerly current is also periodical, and con- 

 tinues to flow during longer periods than the easterly one. It 

 commences where the other ends, in the Bay of Fundy, and 

 he thinks it generally becomes exhausted on the westerly part 

 of the coast of JMaine, though sometimes he has felt its in- 

 fluence as far south and west as Cape Ann. 



Art. XXVIL— descriptions OP SIX SPECIES OF SHELLS RE- 

 GARDED AS NEW. By J. W. Mighels, M. D., Portland, Maine. Com- 

 municated March, 1343. 



ASTARTE PORTLANDICA. 



A. testa parva, solida, per-inequilaterali ; umbonibus elevatis, approxima- 

 tis, recurvis ; lunula angustata ; intus lividd ; marginibus simplicibus. 



Plate XVI. Fig 2. 



Shell small, solid, rather compressed, very inequilateral, 

 upper part of the anterior margin moderately curved, ante- 

 rior, basal and posterior margins regularly rounded ; beaks 



39 



