68 THE NAUTILUS. 



DALL, WM. H. 



[' 79] Report on the Limpets and Chitons of the Alaskan and Arctic Regions, 



with descriptions of Genera and Species believed to be new. Proc. U. S. 



N. M., pp. 281-344, pi. i-v., 1879. (Republished as Art. IV in " Sci. 



Results of Exploration of Alaska.") 



['81] On the genera of Chitons. Proc. U. S. N. M., pp. 279-291, 1881. 

 ['05 a] A new Chiton from the New England Coast. Proc. Biol. Soc. 



Wash, xviii, pp. 203-204, Sept. 2, 1905. 

 [ '05 b] A new Chiton from the New England Coast. NAUTILUS, xix. No. 



8, pp. 88-90, pi. IV, Dec. 1905. 

 FISCHER, PAUL. 



['87] Manuel de Conchyliologie, etc., Paris, 1887. 

 GOULD, AUGUSTUS A. 



[ '70] Report on the Invertebrata of Massachusetts. 2d. ed. (Binney's) 



Boston, 1870. 



PILSBRY, HENRY A. 



['92] Manual of Conchology, structural and systematic. Vol. XIV. Poly- 



placophora. Philadelphia, 1892. 

 POSSELT, HENRY J. 



['98] GronlandsBrachiopoder ogBloddyr. Conspectus Faun. Groenlandic., 

 i, pp. i-xix, 1-298, pi. 1-ii and map. Copenhagen (?) 1898. 



SARS, G. 0. 



[ '78] Mollusca Regionis Arcticae Norvegias Bidrag til kundskab. om Norg. 

 Ark. Faun., I, pp. I-XVI, 1-466, pi. 1-34 and I-XVIII and Map. Chris- 

 tiana, 1878. 



SOME OBSERVATIONS ON THE OVA OF UNIONIDJE. 



BY L. S. FRIERSON. 



When the ova of those species of Unionidse, with which I am 

 acquainted, are first noted in the marsupia, they are spherical in 

 shape, and consist of a single mass of yolk, surrounded with a clear 

 fluid, probably albumen, all confined in a spherical egg-shell mem- 

 brane. Soon after fertilization takes place, the yolk undergoes 

 segmentation, and goes through a " mulberry " stage, and finishes 

 with the familiar glochidium. Several interesting facts have been 

 noted, which may prove of interest. Some young ova of a Quadrula 

 trapezoides Lea were under observation, and being called oft' a short 

 time, on my return I noticed that some of the ova had changed their 



