14 BULLETIN 111, UNITED STATES NATIONAL MUSEUM. 



Cadulus (Cadulus) platensis, new species, page 147. 

 Cadulus (Cadulus) podagrinus, new species, page 148. 

 Cadulus (Cadulus) halius, new species, page 149. 

 Cadulus (Cadulus) tersus, new species, page 149. 



GEOGRAPHICAL DISTRIBUTION. 



The following table sets forth the geographical and depth ranges 

 of all the species and subspecies enumerated in this paper. To 

 interpret the records some allowance must be made for the meager 

 information we possess in regard to many of the species. The area 

 under consideration is very great, including many thousand miles . 



of coast line and vast expanse of ocean, where the extremes of tem- 

 perature and salinity are met. In all this diversified area but few 

 rather restricted regions have been thoroughly explored. The entire ,] 



coast from the Mississippi Delta to Colon and thence along the Carib- j 



bean shores of South America is almost unknown. The few records \ 



we have from its continental slope are insufficient for conclusive ) 



generalization. The number of dredge hauls from the entire South ! 



American coast is actually less than those made within a square of 

 20 or 30 miles off Cape Hatteras. The same is almost true of the 

 archibenthal belt about the Antillean Islands. In the very few areas 

 where intensive collecting has been done a number of Scaphopods 

 have been discovered which, upon our range list, must appear to be ! 



as of a particular locality only, while some others connect specifically 

 a thousand miles away without any intermediate record. Thus 

 many vagaries of distribution are presented which would likely be 

 explained away by a fuller knowledge of actual facts. Our table is 

 truthful as far as it goes, but it can not always tell the whole truth. 



A possible source of error may arise where the continental slope 

 drops swiftly into profound depths, and especially where such declivi- 

 ties are swept by an oceanic current. This condition obtains off the 

 Yucatan Banks, along the shores of Cuba, and probably in many 

 other Antillean localities where steep depth gradients are the rule 

 rather than the exception. Thus, species living near the upper edge 

 of a continental slope (usually a rich life zone) may easily have their 

 dead shells carried the few miles necessary to deposit them upon the 

 ocean floor. Fish no doubt consume vast quantities of Scaphapods 

 and occasionally eject their shells at considerable distances. 



Despite the poverty of our data and the margin of error in our 

 records it is, nevertheless, possible to draw some definite conclusions 

 from the table. 



1. A cold-water group (D. stimpsoni, occidentale, georgiense, ensi- 

 culus, and S. lohatum) belonging to a far northern range and all 

 having East Atlantic affiliations, persist south of Cape Cod and occa- 

 sionally even to Hatteras. In all such cases their station depths are 

 sufficient to furnish the degree of cold necessary for their economy. 



