134 



INTRODUCTION. 



Genus — Lingula, Brugiiiere, 1789. 



Type~L. anatina, Lamarck. Int., PI. IX, figs. 27G— 279. 



Patella, Gmel. (part). 

 Pinna (part), Chemnitz. 

 Mytilus, Billwyn. 

 Lingula, of all modern Authors. 



Shell thin, sub-equivalve, equilateral, more or less elongated, oval or sub-pentagonal, 

 tapering at the beaks, widened at the pallial region ; valves unarticulated, held together 

 by the adductor muscles ; both slightly convex, but depressed, beak of the valve more 

 pointed and rather exceeding the other in length ; surface smooth or concentrically striated, 

 and covered by an epidermis. ^;ef?;^«/ attached to submarine bottoms by the means of a long 

 Fig. 50. peduncle passing out between the beaks of the two valves ; no calcified sup- 

 ports ; on each side of the mouth is situated an elongated subspiral arm, 

 fringed exteriorly with numerous cirri. In the interior, several muscular 

 impressions are visible ; close to the beak are the conjoined depressions 

 left by the pedicle muscle (a), under these, and laterally near the margin 

 of the shell exist two large impressions due to the decussating muscle which 

 produces the sliding action of the valves on each other (b), and towards 

 the centre are situated two small oblique oval scars, caused by the posterior 

 pair of adductor muscles (c), which in the larger valve are divided by a 

 blunt rounded projection, and in the smaller by an elongated mesial elevated crest ; under 

 the last described impressions another triangular depression was occupied by the com- 

 bined extremities of the anterior pair (d) : shell almost entirely composed of laminae of 

 horny matter, perforated by minute tubuli. 



Obs. Professor Owen having described the anatomical characters of the animal, I shall 

 only notice that Cuvier was the first author who pointed out the internal dispositions of 

 this remarkable genus,^ and which prompted him to create a special class, to which 

 he applied the term Brachiopoda. 



Geol. ran(/e. — This genus is among the most ancient forms of animal life ; it first 

 appeared in the lowest Silurian epoch, and has continued uninterruptedly to the present 

 period, where it is still represented by several forms living on the shores of tropical 

 regions, and varying so little in external aspect through its long continued existence as 

 to render specific distinctions often difficult to appreciate. 



Exavijjles : L. anatina, Lam. ; Mans, Swains ; Audehardi, Brod. ; semen, Brod. , 

 albida. Hinds j Bximortieri^ Nj^st; ovalis. Sow. (non Reeves); Lewisii, Sow.; Beanii, 



A 



Lingula anatina. 



1 Memoir sur I'Animal de la Lingule (L. anatina, Lam.), Mem. du Museum, vol. i, p. 69, pi. vi. 



1802. 



■^ In Part I, this species is every where erroneously spelt Dumontieri. 



