T. Bland on the Geographical Distribution of Mollusca. 395 



The " Catalogue of Shells collected at Panama,^^ (New York, 

 1852,) by Professor Adams, now claims our attention. 



The Preface commences with the following passage : — 



" The reader of the Introduction to this work, and of Dr. 

 Gonld's Introduction to his great work on the shells of the Uni- 

 ted States Exploring Expedition, may be struck with the coin- 

 cidence of opinions relating to the geographical distribution of 

 species, and to errors in the statement of habitats, and in the dis- 

 tinctive characters of species. Tlie coincidence is so exact, that 

 it might naturally be supposed that these opinions originated in a 

 single source. Such was their origin : but that source was the 

 book of Nature. It was not until after both Introductions had 

 been written, that opportunities occurred for a free interchange of 

 views with Dr. Gould. It is therefore with the liveliest satisfac- 

 tion that we derive assurance of their correctness both from the 

 extent and accuracy of Dr. Gould's knowledge, and also from the 

 coincidence of the results of independent investigations." 



Professor Adams visited Panama at the end of 1850, and in the 

 space of six weeks collected there, and in the immediate vicinity, 

 and at the Island of Taboga, no less than 516 species of Mol- 

 lusks, of which 158 are described in the Catalogue as new, and 

 64 are enumerated as undetermined. He states that besides the 

 object of making additions to the Museum of Amherst College, 

 he desired "to ascertain, with the certainty of personal observa- 

 tion, what and how many species of shells exist at Panama. 

 Having formerly collected about 500 marine species in Jamaica, 

 near the centre of the Caribbean Zoological Province, it was 

 thought that a comparison of these authentic materials would not 

 be without interest." 



In the Introduction, we have the result of such comparison; 

 but our limits will admit of little more than the following extract : — 



" Panama is situated near the middle of a well defined marine 

 zoological province. Perhaps none of the species of testaceous 

 Mollusca (to which part of the Fauna our remarks are limited) 

 which inhabit the neighboring seas, exist south of 22° S. lat., or 

 north of 28° N. lat., or west of the Gallapago Islands. All of the 

 few examples of species, which are supposed to have a wider 

 range, are more or less doubtful. Some species which inhabit the 

 northern part of the province, and others which inhabit the south- 

 ern part, may overlap the boundaries between this and the adja- 

 cent provinces. But these species present only the usual difficulty 

 in attempting to define the limits of a zoological province. 



The mt)st definite and satisfactory method of defining the limits 

 of this province, is to place the boundaries at the extreme limits 

 of the range of about 99 per cent, of the species which inhabit 

 its middle regions. Thus it will be seen that several of the spe- 

 cies which inhabit Panama also inhabit Gnaymas, in the Gulf of 



