OBSERVATIONS ON LIVING SOLENOMYA 



(VELUM AND BOREALIS). 



EDWARD S. MORSE. 



The genus Solenomya, represented by a few species, is widely 

 distributed throughout the world. It has been found on the 

 east and west coast of North America, in West Africa, the 

 Mediterranean, the Canaries, Australia and New Zealand. The 

 few species agree in almost every detail but vary greatly in size. 

 Our two species, 5. velum and 5. borealis, are one inch and three 

 inches long respectively. S. bartschi from Manila is eight and 

 one half inches in length. The species vary greatly in the 

 proportional number of individuals. 5 1 . velum is at times thrown 

 up by thousands on our beaches, S. borealis is rarely found. 

 5. grand is, which departs more widely from the type than the 

 others, is known by two specimens and a few fragments, while 

 the gigantic 5. bartschi is represented by a single specimen. The 

 various species have without exception a long semi-cylindrical 

 shell, rounded at both ends, a long and almost straight hinge 

 margin. They all have radiating ribs with an apparent inter- 

 space in the series in which however a faint rib may be detected. 

 They all have a highly polished periosteum which runs far 

 beyond the border of the true limy shell, and to which the mantle 

 with its curious system of muscles is closely adherent. The 

 radiating ribs are continued through the overlapping periosteum 

 by a marked thinning of the substance and Professor Drew 

 discovered that when the periosteum folds inward as the valves 

 close these thin areas fold in a plaited manner. In the dry 

 state these interspaces often split and the substance being very 

 brittle it is hard to preserve unbroken in cabinet specimens. 

 The various species vary from a light yellowish brown to a dark 

 brown and even a tar color. The shell within is grayish blue or 

 lead color in S. borealis, purplish white in S. velum. 



Pelseneer 8 has shown that Solenomya has a very primitive 



form of gill and Mitsukuri 7 had previously studied the gill of 



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