7° 



CURRENT LITERATURE. 



VARIATION. 



Shell-bearing Mollusca of Michigan. (Naut. p. 31-35, 1892.) 



Mr. Bryant Walker has an interesting article on the Limnaidce of Michigan, 

 illustrated with eight figures. 



New Varieties of American Mollusca. (Jy. Conch., 1892.) T. D. A. 

 Cockerell. 



New Variety of H. arbustorum. (Sci. Goss., p. 187, 1892.) K. Wiggles- 

 worth. 



Notes on Varieties. (Brit. Nat., p. 153, 1892.) W. A. Gain. 



SPECIAL FAUNA AND DISTRIBUTION. 



Anodonta and Glabaris. (Zool. Anz., pp. 474-84, 1891, and pp. 1-5, 1892.) 



Dr. von Ihering divides all the large freshwater Lamellibranchs (Najades) 

 into two very distinct families, viz. , Unio)udie and Mutelidce according to 

 the nature of their larva. The genera such as Unio, Anodonla, Sec, belonging to 

 the first, have a larva called " glochidium " with an equally-valved shell 

 covering the whole animal, while the Mutelidce possess a larva of a very different 

 nature the shell being small and the body of the animal composed of three distinct 

 paits. 



The author then draws attention to the very close relation between the South 

 American genus Glabaris and the African Spatha, and concludes with some 

 remarks on distribution which are of great interest, as they differ very materially 

 from the views of Dr. Wallace, perhaps the greatest living authority on the 

 Geographical Distribution of animals. 



Anodous according to Dr. von Ihering occur in the Pakearctic, Nearctic, and 

 possibly the Oriental Region, but are absent from the Neotropic and Ethiopean, 

 where Glabaris and other Mutelidic take their place. The Unionida and Mutelidce 

 of North America show a relationship with those of Europe and Asia, but those 

 of South America consist of two separate elements which were produced by a 

 totally different distribution of land and water during the secondary period. 



The first, which he calls the Chileno-patagonian element, is related to New 

 Zealand. The other has no connection with North America, but only with Africa, 

 and the author believes that there existed without doubt a land-connection between 

 Africa and South America, and between the Chileno-patagonian continent and 

 New Zealand during the Mesozoic Period. South America, as we find it at 

 present, has originated from a fusion of various continents during tertiary times. 



Molluscan Fauna of Porto Rico. (Journ. de Conch., pp. 1-71, 1892.) 



H. Crosse has one of his admirable and exhaustive articles on the land and 

 freshwater mollusca of Porto Rico. He enumerates 128 species, 105 being land 

 and 23 freshwater. The former analyse as follows: — Glandina 5, Selenites 1, 

 Hyalinia 6, Helix 19, Gteotis 3, Clausilia, Spiraxis, Simpulopsis, Pineria and 

 Pseudobalea, 1 each, Bulimulus 7, Macroceramus 3, Cylindrella 3, Pupa 2, 

 Strophia 2, Leptinaria 3, Stenooyra 10, Succinea 3, Vagiiiula I, Megalomastoma 



3, Choanopoma 3, Cistula 3, Chondropoma 4, Uelicina 9, Stoastoma 1, Melampus 



4, Pedipes 1, Blauneria 1, Truncatella 1. Removing the last four genera, which 

 can hardly be considered to belong to the land fauna proper, we obtain a total of 

 98 species. The freshwater species are : — Limmca I, Planorbis 10, Ancylus 2, 

 Physa 1, Aplecta 1, Amnicola 1, Ncritina 3, Dreissensia I. Eupera 2, and 

 Cyrenella 1. 



The affinities of the island are, in the main, with San Domingo, of which it is, 

 Geographically speaking, a fragment. It has also relations, less well marked, 

 with Jamaica and Cuba, and, to a still less extent, with the Lesser Antilles. The 

 presence of a single Clausilia, and of the genus Gteotis is very remarkable ; they 

 occur here alone in the West Indies. 



