8 



Thracia Couthouyi. T. parva, alba, solidula, orbiculato- 

 ovalis, sub-8equilateralis, compressa, antice angustior, rotun- 

 data ; postice late truncata ; striis concentricis ineequalibus 

 rugosa ; sinus siphonalis latus. Ossiculum minutissimum. Long. 

 .7 ; lat. .54. Hob. Massachusetts Bay. 



Certain forms of T. distorta of Europe approach this shell in 

 external appearance, but differ totally in the hinge. Our species 

 has no prominent cartilage plate at the hinge. From our native 

 species, T. Co7iradi and T. truncata^ this is easily distinguished ; 

 from the former by its compressed form and posterior breadth, 

 and from the latter by the position of the beaks. 



I take pleasure in being able to dedicate to Capt. Couthouy a 

 species belonging to a family which he has done so much to 

 elucidate, and to a genus which he has enriched with species. 



This shell I first took some years since from a fish taken in 

 fourteen fathoms, some miles east of the Boston Lighthouse. It 

 has since been taken from fishes caught in the Bay, by Messrs. 

 Tufts and Haskell, of Lynn ; and I have recently obtained several 

 specimens from twenty fathoms, eight miles east of Scituate. 



Spirialis Gouldii. T. ovato-globosa, vitrea, pertenuis, pel- 

 lucida, laevissima, arete et profunde umbilicata ; spira conoi- 

 dea ; anf. 7, lineis minutis volventibus, impressis, remotis in- 

 sculpti ; anf. ultimus magnus ; apertura spiram sub-sequans, 

 antice obtusa. Long. .1 ; lat. .075. Hah. Coast of New Eng- 

 land, north of Cape Cod. 



This species being the first Pteropod discovered on our coast, 

 I respectfully dedicate it to Dr. Gould. It belongs to a genus of 

 minute sinistral shells, the true character of which has but 

 recently been detected. 



In the two past years specimens have occurred in Massachu- 

 setts Bay, from February to April. 



Anaperus unisemita. Body covered with minute calcare- 

 ous grains, about two inches in length, somewhat cylindrical, 

 tapering at both extremities, and covered with numerous short 

 suckers, which, on one side, are arranged somewhat irregularly 

 in a double row. This row is often separated from the rest of 

 the suckers by a smooth space on each side. The tentacula 

 are very small ; they are ten in number, two of which, at the 



