THE GENERA OF THE BRACHIOPODA, 



i. 



BEACHIOPODA INAKTICULATA. 



Valves inarticulated; intestine terminating in an anus on one side 

 of the body, shell substance largely phosphatic. 



The foregoing characters bring into association a well defined 

 assemblage of these organisms, but, while generally applicable 

 throughout the group in expressing the fundamental distinctions 

 from the more abundantly developed Brachiopoda Articulata, 

 there often appear, in forms which can not be separated from 

 such association, tendencies to transgress these limitations in 

 various directions. For example, articulation of the valves was 

 approached, if not effected, in the linguloid Barroisella, in 

 Spondyloboltjs, and, perhaps also, in Neobolus and Trimerella. 

 In Crania, according to the determination of Joubin, the anus 

 opens in the median line of the body ; and in various genera, 

 Crania, Pholidops, Trimerella, etc., there is evidence that the 

 substance of the shell was essentially, or altogether calcareous. 



For this division of the Brachiopoda it seems preferable to 

 adopt Professor Huxley's term, Inarticulata, as having the 

 advantage of euphony and simplicity. Other writers have made 

 use of terms with different significations, all having precisely the 

 same scope. Professor Owen, in 1858, proposed the term Lyopo- 

 mata (A6w and 7rd>/aa), essentially the Greek equivalent of Inarticu- 

 lata, and of Bronn's Ecardines. The last named author also 

 suggested the term Pleuropyoia, derived from the lateral position 

 of the intestinal perforation ; while King's term, Tretenterata, 

 indicates that the existence of an anus is to be regarded as the 

 essential character. 



Lingula, Bruguiere. 1789. 

 (Plate 1, Figs. 1-9). 



Shells sub-equivalve ; elongate-ovate, sub-quadrate or sub-tri- 

 angular in outline ; broad over the pallial region, cardinal slopes 

 more or less conspicuous ; slightly gaping at both extremities. 

 Brachial valve somewhat the shorter, and with a slightly 

 thickened hinge-line. Surface of the shell smooth, or concen- 

 trically and radiately striated. Animal attached by a long, mus- 



94 



