4 BULLETIN OF THE 



ing, with his head away from the observer, on a plane at right angles to 

 the line of sight. 



The figures after the references to the plates indicate the longest 

 diameter of the shell in the position in which it is figured, whether this 

 be height or diameter actually, unless it be otherwise stated. As a 

 rule " alt." is prefixed to statements of dimension which refer to height 

 of the spire, and " lat." or " diam." to the measurements taken at right 

 angles to the axis of the spire. 



The nomenclature adopted is based on the rules of the British Associa- 

 tion, as illustrated by the Report of the American Association in 1877, 

 and the subsequent contributions of De Candolle and the American 

 Ornithologist's Union. I have not seen any more recent discussions of 

 the subject which go far enough into it to be of much importance. 

 Such a report as that of the Bologna Geological Congress is so inade- 

 quate as to carry no weight ; the so-called rules being essentially su- 

 perficial and insufficient to meet the needs of the conscientious student 

 of nomenclature. 



The relation of the deep-sea fauna to the fauna of the Tertiaries 

 is more intimate in some respects than that of the Tertiaries to 

 the recent fauna of the litorale. A number of genera and subordi- 

 nate groups hitherto known only from the Tertiary deposits will be 

 found enumerated among the forms collected by the " Blake " and 

 " Albatross." 



The Index will contain references to the species mentioned in both 

 Part I and Part II, and the plates are continuously numbered in the 

 two papers. The preliminary descriptions of Bulletin M. C. Z., Vol. IX, 

 No. 2, 1881, which are not reprinted, were provided with an index of 

 their own. 



For the student interested in the fauna of the southern coasts of the 

 United States, this report will contain more new information than has 

 appeared in any single publication for many years. The writer hopes 

 that it may stimulate in some measure the interest in that fauna which 

 its richness, its possibility of novelties to come, and its relations with 

 the fauna of the Antilles, may reasonably lead us to expect. There is no 

 department of biology where more remains to be done than among the 

 Mollusca, and it is in the power of any good observer, whether scientifi- 

 cally trained or not, to add to the sum of our knowledge, and materially 

 aid in the reformation of the present unsatisfactory systems. 



Washington, D. C, June, 1888. 



