ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 571 



A. glaciata Michaelsen was found south of the Tierra del Fuego, and 

 A. septentrionalis Huntsman on the west coast of Canada. 



Simple Ascidians of New England and Adjacent Coasts.* — Willard 

 G. Van Name deals with thirty-four species, distributed in six families 

 and twelve genera. The most interesting form is Traustedt's genus 

 Bostrichobranchus, which is evidently derived from the genus Eugyra 

 Aider and Hancock, from which it differs in the multiplication of 

 the infundibula of the branchial sac. According to the author, it is 

 the most highly specialized genus of Ascidians. The peculiarities of the 

 branchial sac are described at length. One species of Tethyum (Styela), 

 namely, T. mortensmi Hartmeyer, is unusual in the degree of reduction 

 of the folds of the branchial sac. A small species of the family 

 Ctesiridae (Molgulidas), namely, G. singularis sp. n., has the gonads of a 

 peculiar form, the folds of the branchial sac reduced to an unusual 

 degree, and the tentacles unbranched. The last-mentioned character 

 seems to be unique in the family. 



INVERTEBRATA. 



Mollusca. 



Molluscan Fauna of Florida Oligocene.f — W. H. Dall gives an 

 account of the Molluscan fauna of the Orthaulax pugnax zone of the 

 Oligocene of Tampa, Florida. Many of the fossils have been replaced 

 by casts of pure silex, and are famous for their beauty. These are of 

 particular scientific importance as furnishing a key to the little under- 

 stood succession of the Tertiary beds which fringe the islands of the 

 West Indies and the encircling continental shores. The number of 

 species and varieties of Molluscs now known from the zone is 312, 

 and nearly two-thirds of these are peculiar to it. No fewer than 219 

 species were new to science when the zone was first explored by the 

 United States Geological Survey, and ninety-five of these are described 

 in this monograph. 



7- Gastropoda. 



New Arctic Opisthobranch.J — Nils Hy. Odhner describes Ptisan al a. 

 limnseoides g. et sp. n., known first from Quaternary shell-deposits, and 

 afterwards from specimens from Spitzbergen (dredged by Torell in 1858). 

 A description is given of the shell, the radula, the alimentary canal, the 

 nervous system, the sense-organs, and the gonads. The rhinophores of 

 Opisthobranchs are particularly discussed. Although derived from a 

 primarily indifferent cephalic lobe, they are not absolutely homologous 

 throughout, for they have arisen from differently specialized parts of 

 that lobe. The open rhinophores of Ascoglossa cannot be derived from 

 the cylindrical foliated or smooth ones of iEolididae. In the structure 

 of the radula, in the absence of parapodia, operculum, tentacles, jaws 

 and gizzard-plates, and also in the nervous and genital systems there is 



* Proc. Boston Soc. Nat. Hist.,xxxiv. (1912, received 1915) pp. 439-619 (31 pis.), 

 t Smithsonian Inst. Bull. No. 90 (1915) pp. 1-173 (26 pis.). 

 X Arkiv Zool. viii. (1914) No. 25, pp. 1-18 (1 pi.). 



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