32 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



NOTE. 



Since the preparation of this paper, Dr. Walter Stempell's paper, 

 entitled Beitrage zur Kenntniss der Nuculiden (Fauna Chilensis, Heft 

 2. Zool. Jahrbucher Supplement IV, 1898), has appeared. While it 

 seems that Dr. Stempell has not worked directly upon Yoldia, his 

 paper treats in detail on the anatomy of related forms, and can easily 

 be made the basis of interesting comparisons. It is a point of much 

 interest that closely related forms of this group, even two species of 

 the same genus, may differ markedly in some not unessential details. 

 This probably accounts for most of the differences recorded in these 

 papers. 



In only two points do our papers seem to conflict. On page 355 

 Dr. Stempell, in speaking of the hypothesis* that the unpaired tentacle 

 is homologous with the tentacles fringing the postero-ventral margins 

 of the mantle, objects on the ground that Leda sulcata, while possessing 

 the unpaired tentacle, has no marginal tentacles along the posterior 

 portion of the mantle. It seems to me that the evidence cited, begin- 

 ning with page 6 of the present paper, will outweigh this objection. 



The other point of difference lies in the probability of the modified 

 foot of these forms acting as a creeping organ. Dr. Stempell has not 

 studied the animals alive and relies on published evidence that I 

 cannot fully accept. (See Stempell's paper, page 374, and the present 

 paper, foot-note, page 9.) 



* Brooks and Drew. Notes on the anatomy of Yoldia I. Johns Hopkins Univ. 

 Circulars, No. 126, 1896. 



