INTRODUCTION. Panama Shells. 19 



the California travel. Littoral explorations however, produce 

 a greater amount of results in a short time. 



It has become so fashionable to undervalue a knowledge 



o 



of the shells of Mollusca, because the shell is only a part of 

 the animal, that we shall probably be censured for having neg- 

 lected to observe the soft parts. But non omnes omnia pos- 

 sumus, especially with only six weeks time. It will not be 

 denied that the existence of the species is sufficiently proved 

 by collecting the shells, nor that their geographical distribu- 

 tion may be learned, when we ascertain where they exist, 

 nor that habits of station may be learned without dissection, 

 although this is indispensable for some objects, nor that the 

 recondite questions on the origin of the species are intimately 

 connected with the facts of distribution and station, nor 

 even that the number of species in a given region and the 

 abundance or scarcity of individuals are interesting features 

 in the plan of creation. In short, it will not be denied that 

 the sum total of Zoology consists of parts, and that the per- 

 fection of the whole rnay be better secured by a division of 

 labor. "We hope therefore, that the following results, not- 

 withstanding the magnitude of the deficiencies, will be re- 

 garded as somewhat better than the only alternative before us, 

 that of the stay-at-home collectors. 



\ The situation of Panama is eminently favorable for the 

 collection of shells. At the head of an extensive bay, whose 

 waters well merit the appellation of Pacific, it stands also at 

 the head of a reef, which furnishes a great variety of station 

 for the mollusks. Our hotel was within a minute's walk of 

 this reef. In front of the city, the reef consists of ledges of 

 trachytic rocks, with flat and concave surfaces, with gently 

 sloping, precipitous, or shelving sides : in other parts exten- 

 sive tracts are covered with loose fragments of rock, the diffe- 

 rent sizes of which, and the different degrees in which they 

 are buried in sand, or in which they have open spaces be- 



