INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 485 



of these localities in summer. In April, May, and June, the cod and 

 haddock resort in large numbers to the banks and re'^-fs off Stonington, 

 Watch Hill, No Man's Land, and other similar places, but are quite 

 unknown there later in the summer. 



In consequence of the varying temperatures of the currents which 

 alternately pass over certain of these localities, there is a very peculiar 

 admixture of northern and southern species, side by side. This is par- 

 ticularly the case on the reefs between Watch Elill and Fisher's Island, 

 where the southern Astrangia Dame is associated with the northern 

 Alcyonium carneum, Cribrella sanguinolenta, and many other northern 

 forms. 



The temperature of the bottom-water during the last of August and 

 first of September was found to vary from 57° F. to G3°, in sixteen to 

 twenty-nine fathoms off Martha's Vineyard and Buzzard's Bay, (see 

 chart,) '^he surface temperatures were at the same time 02° to 64:°, and 

 occasionallj^ as high as 67°, when affected by warmer currents. 



IV. 1. — Species iNiiABiTiNa rocky shores of the open coast. 



The principal localities under this head at which we have made col- 

 lections are No Man's Land, Cuttyhunk Island, Gay Head, and Watch 

 Hill, Rhode Islaiid. Dr. J. E. Leidy has published a partial list of the 

 species found at Point Judith,* and we have more or less information 

 concerning the fauna of several other similar localities. In all these 

 places the assemblage of animals is nearly the same, and in general not 

 very different from what we find on the rocky shores of the sounds and 

 bays, (see p. 303.) A large part of the species of these shores have 

 therefore, already been mentioned in connection with the fauna of the 

 bays and sounds. 



There are, however, many species that are characteristic of the latter, 

 which are found but rarely, or not at all, on the colder and more ex- 

 posed outer shores; and these are characterized by the abundance of 

 some northern species which are rare or wanting on the inner shores, or 

 which occur there only in winter. 



Among the most abundant species of shells are Purpura lapUIus, (p. 

 306, Plate XXI, figs. 118, 119;) Littorina palUata, (p. 305, Plate XXLV, 

 fig. 138;) L.rudis, (p. 305, Plate XXIV, fig. 137;) Acnuva te-studinalis, 

 (p. 307, Plate XXIV, figs. 158, 159;) and Lacuna vincta, (p. 305, Plate 

 XXIV, fig. 139,) all of which occur adhering to the rocks or algfe, even 

 in the most exposed situations. These are all hardy northern si»ecies. 

 which extend their range to Greenland or beyond, and although all of 

 them are to be found, more or less frequently, on the inner shores, tbey 

 are there less abundant and generally of smaller size. The Littoritia 

 IKiUlata is extremely abundant on the Fucus^'Aud individuals were found 

 at Watch Hill, copulating, April 12. The Lacuna vincta breeds still 



* Journal of the Academy of Natural Sciences of Philadelphia, 2d series, vol. iii, 

 1855. 



