NATURAL SCIENCES OF PHILADELPHIA. 133 



There can be no doubt as to the validity of this species, as it widely differs 

 iu the number of its rays from all except one otherspecies of Priacanthus, and 

 especially from the formerly known American ones. The only species which 

 resembles it in the number of the rays of the fins is a Japanese species the 

 Priacanthus niphonim of Cuvier and Valenciennes, and the Fauna Japonica. 

 In other respects also the Japanese and North American species are closely 

 related. The f >rm is nearly similar but the height even greater in ours than in 

 the Priacanthus niphonius, and consequently exceeding that of any other 

 known species of the genus ; the scales of the body and head are very rough ; the 

 ventral fins in the young, at least, entirely blackish ; the spinous portion of 

 the anal fin is also very dark. It is probable that the species undergoes a 

 change of color somewhat similar to the Priacanthus niphonius. 



The discovery of three new species of fishes on the coast of Rhode Island, 

 all representing forms almost entirely confined to warmer seas, in such rapid 

 succession, is an event of no little interest and importance. The specimens 

 obtained were all young ; single examples only were found of the Sarothrodus 

 ( Chato'lon auct.) maculo-cinctus and the Priacanthus, and two of the Hypor- 

 thodus flavicauda. They were all doubtless brought to the New England shores 

 by the Gulf Stream, which runs near the Rhode Island coa-t, and in which 

 the traveller often finds small fishes, as well as other animals, of which the 

 Isopod Crustacean, described below by Dr. Stimpson, is an example. None 

 of the three species of fishes previously mentioned have yet been seen in the 

 West Indian seas, where they will undoubtedly be hereafter found. It is 

 important also to compare the discovery of these fishes on our own northern 

 shores with the discovery on the Scandinavian and Greenland coasts of forms 

 equally characteristic of the tropics. In another article I will allude to the 

 analogy between the denizens of the Carribean and Japanese seas. 



On aa oceanic ISOPOD found naar the south-eastern shores of Massachusetts, 



BY VVM. STIMPSON. 



In the summer of 1859, while cruising among the south-eastern islands of 

 Massachusetts in company with my friends Dr. Slack and Mr. Ordway, we 

 approached the shores of the beautiful island of Martha's Vineyard the Isle 

 of Wight of New England. When becalmed in the Vineyard Sound north of 

 Gay Head, we were occupied in observing the small medusae and other pelagic 

 animals which appeared near the surface of the water. Among them we no- 

 ticed some pretty blue isopods quite new to our shores, which reminded 

 me of forms which I had met with in the temperate parts of both great oceans. 

 They were swimming at the surface and could be easily distinguished from 

 the deck of our boat, even at some distance, by the ripple they made in their 

 progress. Several of them were caught, and found to be Idothece of that 

 oceanic type which has the habits of the miniature sailors Physalia, Velella 

 and Janthina, which are occasionally cast upon our south-eastern shores. It 

 proves to be 



Idothea robosta Kr. 



Body strongly convex, two and two-thirds as long as broad, and broadest 

 at the fifth thoracic segment ; lateral outline convex at the thorax, but some- 

 what concave at the abdomen. Surface pubescent. Inner antennae reaching 

 to the penultimate joint of the peduncle of the outer ones, which are less 

 than one-half the length of the body. Thoracic segments protuberant, and 

 laterally somewhat rugose ; their epimera large, distinct and rather sharply 

 projecting. Abdomen strongly three-jointed, with partial separation of a 



1862.] "" 



