2 CRUSTACEA. 



author deems it incumbent to state that the Crustacea constituted one 

 out of three extensive departments under his charge, Geology and 

 Zoophytes, reports on which subjects are already published, having 

 occupied a large share of his time and labours. Moreover, the unfor- 

 tunate wreck of the Peacock on the Columbia bar sacrificed all the 

 collections made through two seasons in the South Pacific, ranging 

 over the ocean from the Paumotus to the Navigator Islands and also 

 to the Kingsmill Group, and only a few dried Crustacea, not included 

 in the packages lost, answer to a detailed catalogue numbering more 

 than a thousand specimens. 



Besides this misfortune, another befell the collections after reaching 

 the country, before the return of the Expedition. A large part of the 

 packages were unfortunately opened, and the specimens prepared, by 

 drying, for exhibition. By this means, the references to the catalogues 

 were to some extent lost, and many specimens were badly injured. 

 Some were rendered wholly unfit for description, especially those of 

 small size, which, without regard to their delicacy of structure, were 

 taken from the bottles containing them and dried, and sometimes 

 transfixed with pins, to the obliteration of many of their characters. 

 Moreover, the larger species were rendered by this process unfit for 

 dissection. 



Notwithstanding these occurrences, the number of new species 

 described in the following pages exceeds five hundred, although in 

 many of those collected we have been anticipated by foreign inves- 

 tigators, owing to the delay in our publications. 



The species embraced belong to every branch of the department of 

 Crustacea, including the minute Entomostraca as well as the higher 

 grades. The subject of classification has therefore come necessarily 

 under consideration. We have also been led for the same reason 

 to a study of the homologies of Crustacea, and have endeavoured to 

 present the parallel relations of species in all the prominent groups. 



