Phylogeny of the Pelecypoda : the Aviculidae and their allies . highly de-veloped foot, which is ca]mble of extreme prolongation, PI. xxvm, fig. 1, and is oftenproduced beyond the edges of the valves to a length equal to the whole height of theshell. While lying on the right valve, the foot is extended through the notch close un-der the hinge line and is attached by a sucker-like action to the glass, shortening itslength. It thus drags the shell along on its right side. The motion is very rapid andthe little creature quickly passes over a considei-able distance. Shells were frequentlyobserved
Phylogeny of the Pelecypoda : the Aviculidae and their allies . highly de-veloped foot, which is ca]mble of extreme prolongation, PI. xxvm, fig. 1, and is oftenproduced beyond the edges of the valves to a length equal to the whole height of theshell. While lying on the right valve, the foot is extended through the notch close un-der the hinge line and is attached by a sucker-like action to the glass, shortening itslength. It thus drags the shell along on its right side. The motion is very rapid andthe little creature quickly passes over a considei-able distance. Shells were frequentlyobserved to clap as in the adult; but they did not SAvim by this means and it is quite jjos-sible that they weie not capable of doing so, as special features of the mantle whichserve the adult in swimming were not yet developed. The foot is so mobile and exten-sible that it may be twisted and turned in any direction at the will of the animal. Older scallops and the adults lie on the right valve, and are rarely found lying on MEMOIRS BOSTON SOC. NAT. HIST., VOL IV. 45. 334 ROBERT TRACY JACKSON ON THE the left side. This latter position, is clue proliably to an accidental overturning-, whichthe scallop alters at an early opportunity. Professor Hyatt informs me in a letter thathe has examined over three hundred specimens of Pecten irradlans, all of which liehabitually on the right valve. The upper, left valve very commonly is more or less over-grown with algae, but I have never observed them on the lower Iight valve. This habitof lying on the iight valve is characteristic of many related genera as Perna, Spondylus,Plicatula, Hinnites, and Auomia. Patten (53) in his studies of Pecten Jacohmus, saysthat this species which has a deeply concave right valve and a flat left valve, lies habit-ually on the right side, and if turned on the left side in an aquarium, soon rights studies of young Pecten iiradians were interesting on this point. I turned themseveral times on the left valve i
Size: 1579px × 1583px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookidphylogenyofp, bookyear1890
