12 



PALJEONTOLOGY OF NEW YORK. 



.- -9 



FIG 



LittgiiUi paracletusi, sp. iiov 

 Interior of iiediclevalve. 



KlG 9. 



Lingula Mclie^ Hall. 

 Iiiterioi' of bracliial valve. 



of these beds, but is described in 

 the concUiding pages of this work 

 as L. paracleius, sj). nov., has 

 afibrded the most complete and 

 satisfactory representation of tlie 

 system of muscular scars. The 

 pedicle-valve here figured is drawn 

 from a cast of the interior, wliicli 

 shows not only the centrals (h), 

 middle laterals (/c), but the dis- 

 tinctly specialized outside laterals 

 (/), anterior laterals (j), the transmedians (/), and the great umbonal (g). 

 Even the asymmetry of the transmedians (?) is apparent in the unequal 

 size of the impressions, that on the left in the figure (corresponding to the 

 right, when looking into the interior of the valve) being noticeably larger than 

 its correlate. In the brachial valve, the scars are essentially like those in the 

 corresponding valve of J.. Melie, shown in the accompanying figure, but are not 

 placed quite so far back. Here the laterals (/, k) and transmedians (i) are 

 coalesced, and show a tendency to spread transversely over the visceral region, 

 a feature sometimes noticeable in other palaeozoic species, and probably of 

 similar nature to that seen in Barroisella suhspalulata (Plate I, fig. 10). 



As far as the vascular markings of the brachiocoele in the fossil species have 

 been observed, they appear to have been in full agreement with those of the 

 living type. In L. Whilii, L. Elderi, L. punctata, L. cuneata, and L. lamellata the 

 large pallial sinuses are to be seen passing forward from the parietal band, or 

 the position of the compound lateral scars, approaching each other until they 

 nearly or quite meet in front. The outer ramifications from these large trunks, 

 and, in L. Elderi and L. cuneata, the inner also, are discernible. In the brachial 

 valve of L. Elderi are seen the vascular impressions of the pleurocoeles, which 

 lie in the post-lateral portion of the internal cavity, outside the parietal 

 band. In L. Procteri and L. paracletus, the anterior vascular branches appear 

 to radiate from the edge of the central muscles, as though the pallial trunks 



