48 PALAEONTOLOGY OF NEW YORK. 



Authors have suggested various functions for the chambers of the phitforui. 

 LiNDSTR'iM* regarded them as having been occupied by the adductor mus- 

 cles; under this interpretation the arches would be conceived as the 

 result of tlie progressive growth of tlie muscular fulcra or excessive 

 shelly deposition al)Out the base of the muscular bands. Davidson and King 

 conceived them, " from their contiguity to the usual locale of the liver, 

 to be the most likel}- receptacle for the divisions of this organ. "f The same 

 authors have also quotedi from a private letter of Mr. Whitfield, an 

 opinion to tlie effect, that on account of the great size of the muscles re- 

 quired to work these ponderous shells, there would, of necessity, be a displace- 

 ment of the essential organs, and that, under the force of this necessity, the 

 platforms may have been developed to raise these large muscles from the center 

 of the valve, and let the sexual organs pass beneath them. Such suggestions, 

 however, can apply primarily, and in their entirety, only to Trimerella, Lakh- 

 .MiNA, and such forms of Dinobolus in which the platforms are vaulted. These 

 do not constitute the largest, or a iairly representative portion of the group, 

 all the other genera, and Dinobolus usually, having the platform solid. 



In order to apprehend more satisfactorily the functions of these specialized 

 parts of the shell, we mav turn our attention briefly to the relations of the 

 platforms in the linguloid genera, Lingdlops and Lingulasma, to the muscular 

 scars and fulcra in the true Lingula. 



While treating of the genus Lingula, we have adverted to the fact, that the 

 anterior and central muscular scars {k, h, of the pedicle-valve ; j, h, of the 

 brachial) may produce either distinctly localized impressions, indicating the 

 space actually covered by the ends of the muscular bands at the time of the 

 death of the animal, or may be much elongated, extending over nearly the 

 entire visceral region, as seen in L. Whitii, L. Elderi, L. punctata, L. lamellata, 

 and others (see Plates I and IV k) ; these large impressions indicating not cor- 

 respondingly great muscles, but the advancing path of the respective bands as 

 the shell has progressed in growth, only the anterior portion of the scar repre- 



* Om Bfiichiopodenslagtet Trimerella. 

 t On the Tnmcrellida!, p. I'M. 

 I On the Tiiinerellitls, p. 135. 



