vol. 



£"'] PKOCEEDINGS OF THE NATIONAL MUSEUM. 285 



with this explanation it should be clear enough that tbe facts were ob- 

 served and recorded in members of each group, aud that the apparent 

 confusion in the diagnosis resulted from a feeling of conservatism in the 

 matter of subdividing genera; a proceeding which has, of late years, 

 on some occasions been so shamefully abused. 



The researches of the U. S. Fish Commission have added some most 

 interesting aud peculiar species of this family, which are more fully 

 described in another part of this report. The forms not so described 

 have been grouped together here. 



Cetoconcha bulla was described rather fully by me in 1880, aud that 

 description merely requires the addition of the statement that the 

 lamellae described are subtubular and form the lips to the septal ori- 

 fices. In using the term "ventral surface" at that time for the under 

 side of the septum aud "body cavity," the reader will not be misled 

 into the supposition that the visceral mass was the "body" intended; 

 for, though the words may have been ill chosen, the relations of the 

 visceral mass were clearly stated, although the very important relation 

 of the upper chamber to the anal siphon was not understood at the 

 time. 



There is in this species a distinct bunching of the muscular fibers at 

 the posterior outer corners of the septum, from which poiuts they ex- 

 tend in a somewhat radiating manner. The soft parts, though more 

 rotund aud with a different number of septal orifices, resemble suffi- 

 ciently those of Cetoconcha Sarsii Smith, as digrammatized by Pelse- 

 neer. For each orifice two lamellre are usually counted in the report 

 of 188G, as the lips- of the septal orifices generally appear paired aud 

 arched, forming a segment of a circle. In C. bulla, in the anterior series, 

 there are five orifices on each side ; the inner posterior series have three 

 to five and the outer posterior series two, or possibly three, orifices each. 

 The number of posterior orifices is not the same in the two specimens 

 of C. bulla examined. 



In none of the specimens of Cetoconcha examined by me were the 

 inner ends of the four posterior series so widely separated as in Pelse 

 neer's Fig. 9 of Silenia Sarsi. They always seemed closer together, and 

 more evidently radiating from a central elevation on the septum behind 

 the foot. But too much stress must not be laid on the discrepancies of 

 his diagrams, which are not and do not appear to be intended for exact 

 and complete portraits. In this species a trace of the lateral arrange- 

 ment of the siphonal muscles remains, while compared with Cuspidaria 

 the septal muscles are still in a transitional state. 



Cetomya elongata Dall. In the single specimen of this form the 

 branchial areas are composed of lamellae, between which at their bases 

 are narrow fissures, bridged longitudinally by slender fibers, which act 

 as regulators. In this species the two areas are similar, and resemble 

 those of Cetomya tornata Jeffreys, as figured by Pelseueer. 



Cetomya albida Dall. In young specimens of this and other species 



