174 THE AMERICAN NATURALIST [Vol. XL 



obvious ones; the account contains some unquestionable errors 

 and some statements which if correct, do not apply to all members 

 of the genus. 



A step in advance was marked by Dall's successive papers on 

 the limpets of which the first appeared in 1869. These papers 

 deal mainly with the Acmaeida? and although preeminently sys- 

 tematic, contain occasionally anatomical facts of interest and 

 importance. 



The first considerable contributions to the morphology of 

 Acmtea are contained, however, in two papers on the compara- 

 tive anatomy of certain organs of Prosobranchs which issued 

 from the laboratory' of Professor E. Perrier about fifteen years ago. 

 The first of these papers, (Bouvier, '87) dealt with the nervous 

 system; the second, (Bernard, '90) with the pallial organs. Bou- 

 vier ('87, pp. 15-22) gives a full and careful description of the 

 nervous system of Patella and in a single paragraph compares 

 therewith the very similar one of A. testvdinalis. Bernard de- 

 ^ scribes in detail the osphradium and the innervation of the gill 

 in a species of Tectura (Acmsea) and in the same connection fig- 

 ures and describes the arrangement of the principal ganglia in 

 what he calls T. fontainesi. It should be noted that this latter 

 species is without doubt, as I have shown elsewhere, (Willcox, 00) 

 incorrectly named and that the identification of the other, so far 

 as concerns the species, is questionable.- The so called Tectura 

 fontainesi, having circumpallial branchial lamellte (Bernard, '90, 

 p. 217) is of course not a true Tectura (x^cmsea) but may very 

 probably be a Scurria. T. pileopsis, Bernard's other species, is 

 stated by him ('90, p. 217) to have come from Chili but that spe- 

 cies is recorded by Pilsbry (Tryon and Pilsbry, '91, p. 57) as be- 

 longing to the New Zealand, Indo-Pacific, and Australian region. 



The first work in which Acma?a was treated monographically 

 was Haller's Studien iiber docoglosse and rhipidoglosse Proso- 

 hranchier, which appeared in 1894. This deals with one species 

 of Scurria and three of Acniiva and as it treats all the important 

 organs of the body except the shell, it would at first sight seem to 

 render superfluous further work iijx.u the small family of Ac- 

 mseidse. Various statements made hv Ilaller have, however, 

 been the object of vigorous criticism and in other particulars which 



