18 INVERTEBRATA OF MASSACHUSETTS. 



mond-shaped, moderately large. In such a diversity of external 

 character, we must look chiefly to the opercular valves for any 

 constancy of form. These are smooth or faintly marked across 

 with fine lines, that appear as if they were about to be effaced. 

 The two front valves are regularly pointed by the junction of 

 their boundary lines ; they are united by a simple suture, and a 

 profile view shows them to be a little gibbous or keeled at the 

 suture, just before their summits. The other valves are blunt at 

 tip, and are deeply grooved, each side, for the reception of the 

 outer edge of the anterior valves, so as to exhibit a deep notch 

 just below their summit. This notch is the most obvious dis- 

 tinctive character of the species, together with the circumstance, 

 that the tips present no prominent points, and do not diverge. 

 Interior smooth and plain, except that there is a fold answering to 

 each external depressed area. 



Compared with B. rugosus, its exterior is much less rugged, it 

 never attains so large a size, its summit is more simple, and its 

 shape more variable. From this, and from specimens of B. ba- 

 lanoides sent me from England, it differs especially in the sum- 

 mits of the valves. These are better indicated by figures than 

 by description. 



BALANUS ELONGA'TUS. 



Shell white, very much elongated, increasing in width towards 

 the summit ; opercular valves as in B. ovularis. 



Lepas elongata, LIN., GMEL. ; 3213. CHEMN. j Conch., viii. t. 98. f. 838. PENNANT ; 



Brit. Zool., iv. t. 37, f. A. 5. 

 Balanus clavatus, PCLTENEY ; Dorset CataL, t. 1, f. 6. MONTAGU ; Test. Brit., 



10. WOOD ; Index, pi. 1, f. 13. Gen. Conch., t. 7, f. 1. 

 Balanus fistulosus, BRUG.; Encyc. Mtth., 166, t. 164, f. 7, 8. LAM.; An. sans 



Vert., v. 665. 



FIGURE 8. 

 State Coll., No. 251. Soc. Cab., No. 2081. 



The shells to which the above names have been applied, and 

 which have attracted considerable attention, seem, after all, not 

 to be entitled to the rank of species. They are now regarded 

 as elongated varieties of other species, having assumed their pe- 

 culiar shape from the circumstance of their being so crowded as to 

 oblige them to make all their growth in one direction. That this 



