200 



LINGULELLA L-iEVis var. GBANDis, n. var. PI. xv, figs. 1 a-d. 



Lingulella -A- large Lingulella of the form of the species described in Illustrations 



Isevis var. o f ^ ne p auna o f the St. John Group* was found at Escasonie. Only 

 grandis r _ _ * 



described ventral valves were obtained, and with one of them is here described an 



interesting ventral from the same horizon at St. John and which is 

 thought to be of the same species. The valve from St. John shows what 

 appears to be the pedicle, and its sinew within the shell. 



Ventral valve Ventral valve broadly ovate with a bluntly pointed, rather high (but 

 poorly preserved) cardinal area. The valve is thin and is evenly arched 

 down in all directions from the centre. The details of the interior are 

 somewhat obscured by the dorsal valve which was pressed down upon it. 

 Interior. A visceral callus, pointed in front, is outlined ; this shows the 

 position of the cardinal muscles. The transmedian (d) and lateral mus- 

 cles (e) are shown by faint scars and inside them, on each side of the 

 valve a low ridge (/) extending forward nearly to the lateral margins ; at 

 the extremity of these ridges is what appears to be the print of a muscle 

 scar ; it is oval, is within the ridge and directed diagonally forward. 



The sinew of the pedicle appears to be preserved in this specimen as a 

 dark sinuous line, originating at a point (k\ where in ventral valves of 

 several species of this genus, a small scar has been observed, and extend- 

 ing out through the pedicle groove (a). From the beak of the shell it can 

 be traced over the surface of the layer of shale on which the shell is pre- 

 served to the margin of the shale fragment containing the fossil. The 

 sinew or muscle within the shell has a diameter of about ^ mm. The 

 pedicle itself outside of the beak of the shell, is considerably larger than 

 the pedicle groove at the beak ; it is composed of at least three elements 

 a central thread of dissevered particles of black, shining, carbonaceous 

 tissue ; this is perhaps a condensation of the coelon substance. It is en- 

 circled by a space showing but little organic matter ; external to this is a 

 tube of strong black tissue, not shining like the central thread, but of com- 

 pact and continuous substance ; external to this tube, there appear traces 

 of organic matter which may be the remains of a fleshy and perishable 

 covering. The diameter of the pedicle is about f of a millimetre near the 

 pedicle groove ; the part of the pedicle preserved is 3 mm. long. 



Dorsal'valve. The dorsal valve from Escasonie, like that above-described, is quite thin, 

 both at the visceral callus and elsewhere ; it is most strongly arched in 

 the posterior half, but flattened on the lateral slopes (this in so thin a shell 

 may be due to pressure after entombment). The form is broadly ovate 

 but blunted at the umbo. 



*Trans. Roy. Soc. Can. vol. ix, sec. iv, p. 39, pi. xii, fig. 4 a-6. 



