AMERICAN NATURAL HISTORY. 



Prime (Temple). A new species of Pisidium. IV. 1851, 67. (241 

 Nov. sp. Pisidium ventricosum. 



Stimpson (W.). On two new shells from Massachusetts Bay. IV. 



1851, 7. (242 

 Nov. sp. Spiriales Gouldii. Thracia Couthouyi. 



I Stttm 



Stimpson (W.). Remarks on an Ascidian, found in Massachusetts 

 Bay. IV. 1851, 49. (243 

 Nov. sp. Pelonaia arenifera. 



R ABLATES. 



Ayres (W. 0.). Observations upon the Holothuridce of the Atlan- 

 tic coast of North America. — Proc. Bost. Soc. Nat. Hist 

 IV. 1851, 5, 11, 25, 35, 46, 52, 60, 63, 69, 73, 102. (254 



Nov. sp, Botryodactyla (n. g.)grandis, 52, 73. 

 Psolus laevigatus, 25. 



granulatus, 63. 

 Sclerodactyla (n. g.) briareus, 5, 102. 

 Stereoderma (n. g.) unisemita, 46. 

 Synapta tenuis, 11.* 

 Thyonidium elongatum, 60. 



rausculosum, 169. 



* = Synapta Girardii, Pourt. 



Pourtales (L. F.). On the Holothurice of the Atlantic coast of 

 the United States. — Proc. Amer. Assoc. Adv. Sc. V. 1851, 

 8. (255 

 Nov. sp. Anaperus briareus. Holothuria floridana. 



[Holothuria briareus, Les.) Synapta Girardii. f 

 Chirodota oolitica. rotifera. 

 Colochiriis gcaamatus. viridis. t 



j = Synapta tenuis, Ayres. 



J The name viridis having been applied by Lesueur to a 

 species of Holothuria, the author proposes to call the present 

 one S. Bachei, since Lcsueur's II. viridis will no doubt prove 

 to be a true Synapta. 



