15.-A CONTRIBUTION TO OUR KNOWLEDGE OF THE MORPHOLOGY OF 

 LAMELLIBRANCHIATE MOLLUSKS.* 



BY JAMKS L. KELLOGG, PH. D. 



At the direction of Hon. Marshall McDonald, U. S. Commissioner of Fish and 

 Fisheries, 1 nndertook the following work at the Fisli Commission station, Woods 

 Holl, Massachusetts, during the summer of 1891, and while there enjoyed the kindly 

 interest of that gentleman, as well as many attentions shown me by Dr. H. V. Wilson, 

 tlien biologist in charge. I am also much indebted to Dr. E. A. Andrews, of Johns 

 Uopkins University, for aid and advice. I wish to express my appreciation of the 

 attention and counsel given me by Prof. W. K. Brooks while engaged in this work. 



Before I began the work it was pointed out to me by Prof. Brooks, of Johns Hop- 

 kins University, that the study of lamellibranch anatomy had been carried on almost 

 entirely by means of dissections, which are difficult to figure or describe satisfactorily, 

 and that comparatively little use had been made of sections. I hope to show not only 

 that the anatomy of a single form may be easily described by this method, but that 

 the comparative anatomy of various forms may be readily demonstrated. 



It is interesting to notice, in connection with this use of sections, that the great 

 amount of labor required in producing such a work as Deshayes' Atlas, Mollusques, 

 has been of little service. It is a very large volume of beautiful jjlates representing 

 dissections ; but, even if they had been jDroperly described, the comparison of special 

 organs of different forms would have been very hard to understand. The cost of such 

 a work also renders it inaccessible. 



Unfortunately I have been able to obtain but very few representatives of this 

 group of mollusks for examination, and consequently do not feel able to attempt very 

 wide generalizations. Since the completion of the present work a full and valuable 

 paper by Prof Paul Pelseneer (No. 17) has appeared, dealing principally with forms 

 other than those here discussed. Much has yet to be done in comparative studies in 

 this group, notwithstanding the great works of Lacaze-Duthiers and others. 



* The principal species of marine bivalve or lamellibrauchiate mollusks treated of in the present 

 paper, which the writer has examined personally, are eleven in number, including six forms of greater 

 or less economic value. The structure of other marine species and of the fresh-water mussels Unto 

 and Anodon is also discussed. The eleven species first referred to are as follows: Mya arenaria Linne 

 (common loiig clam) ; Maetra soridissima Chemnitz (sea clam) ; Venus mercenaria Linn^ (quahog) ; Ven- 

 ericardia borealis Conrad; Solenomya velum Say; Yoldia limafula Say; Area (Argina) pexata Gray; 

 Mytilus edulis Linn6 (common mussel); Pecten irradians Lamarck (scallop); Anomia simplex Verrill; 

 Ostrea virginiana Lister (oyster), 



389 



