117 



To show the anatomy of L. Sdwyni the following figures have been Lingulella 

 drawn, enlarged four diameters from the original types. The pore pits Selwyni> 

 with which the shells are studded and the radiating pits of the mantle rays 

 are omited for greater clearness, but they are quite conspicuous on the 

 valves. 



Lingulella Selwyni, enlarged 4 diameters to show musculation &c. 



a Pedicle groove 6, pseudo-deltidium c, cardinal area d, excurrent 

 branches of the circulatory system e, front of the brachial area f, 

 small tubercles g, cardinal muscle 1 h, anterior adductors ("central") 

 muscle i, transmedian muscles j, anterior laterals k, interior laterals 

 I, exterior laterals p, pedicle muscle ? v.t., vascular trunks v.b., 

 branches of the vascular trunks. 



VENTKAL VALVE. 



Cardinal area. This species has a well developed pedicle groove 

 in the ventral valve, with slopes on each side descending to the deepened 

 central depression, or groove. The pseudo-deltidium is rather narrow, 

 and its sides slope inward as above described, the areal borders are nar- 

 row, and the striae diagonal. The beak is depressed. 



The striae on the cardinal area cannot be due to the contact of the 

 valves in this part as when fully grown the striae of the last growth in 

 the shell are depressed from f to 1 mm. below the plane of the edge of 

 the valve, and the corresponding depression on the dorsal valve would 

 leave these two valves nearly two millimetres apart at the back, hence 

 it seems probable that a ligamental (ileoparietal) band connected the 



