NATURAL SCIENCES OF PHILADELPHIA. 465 



Synopsis of the Recent Species of GASTR0CHJENID2E, a Family of Acephalous 



Mollusca. 



BY GEORGE W. TRYON, JR. 



Linnaeus included in the genera Serpula, Teredo and Pholas, the curious group 

 of shells which form the subject of this memoir and it is not surprising that 

 he should have made such a distribution when we recollect, that until quite 

 recently the animals of these shells were unknown, whilst an obvious external 

 resemblance existed between the tubes of Gastrochama, Rocellaria, etc., and 

 those of Serpula and Teredo, and the valves exhibited a close affinity to those 

 of Pholas. The earlier conchologists, misled by these resemblances, in seve- 

 ral instances referred to different genera the shell and tube of one species. 

 Lamarck assigned to these shells their true position in the system. His family 

 Tubicola included the various species of Aspergillum, Clavagella, Fistulana and 

 Gastrochcena, together with Teredo and Teredina, and excluded the Serpula?. 

 Tcbicola was placed in close connection with the family Pholadaria, to which 

 it is nearly allied not only by external characters, but also by anatomical 

 resemblances and circumstance of habitation. The Lamarckian arrangement 

 and his genera, were adhered to by the few writers who have taken up the 

 study of the family until within the past few years. 



^ Dr. John Edward Gray, in a paper published in the London Zool. Proc. for 

 1858, entitled, " On the Families Aspergillidce, Gastrochcenidce and Ilumphreyiadce," 

 proposed the following classification: 



Family I. ASPERGILLIDJ2. 

 Animal living sunk in sand, or holes in rocks, or shells ; enclosed in a shelly 

 tube in which it resides, and emitting from the front of its mantle a number 

 of tentacles, which are enclosed in tubuli radiating from the edge or disk of 

 the base of the enclosing tube. 



Subfamily 1. PENICILLINA. 



Both the valves of the adult animal imbedded in and forming part of the 

 shelly tubular sheath. The valves of the young animals are early united into 

 one plate. 



Genera. Warnea, Aspergillum, Penicillus, Clepsydra, Arytene, Fcegia. 



Subfamily 2. CLAVAGELLINA. 



Only one valve of the adult animal imbedded in the shelly tubular sheath ; 

 the other free, and movable in the cavity of the tube. 

 Genera. Clavagella (fossil,) Bryopa, Dacosta. 



Family II. GASTROCHJENIDJE. 

 Living sunk in sand or holes in rocks and shells ; enclosed in a shelly tube, 

 in which are contained the free, movable valves. The front of the mantle not 

 provided with any tentacles. The tube of the adult animal closed at the base, 

 and destitute of any slit or perforations; its siphonal end not expanded. 



Subfamily 1. CrLENAINA. 



The tube symmetrical, clavate, free. The animal living free, sunk in sand. 

 Genus Chcena. 



Subfamily 2. GASTROCHJENAINA. 



The tube irregular, attached. The animal living in holes in rocks, shells 

 and other marine bodies. 

 Genus Gastrochcena. 



Family III. HUMPHREYIADJE. 



The animal at first free and covered with two shelly valves, which become 

 1861.] 31 



