LINGULA. 201 



In the interior of the valves may be seen a number of muscular and other impressions 

 with which the palaeontologist should become acquainted, but it would be out of place 

 were we to enter into a minute anatomical description of the animal itself in a work 

 exclusively devoted to fossil species. We will therefore briefly place before the reader a 

 few details only concerning those muscles which have left recognisable impressions in the 

 interior of the valves. It must also be observed that, although Mr. Woodward, Mr. Hancock, 

 Dr. Gratiolet, and others, agree as to the shape and position of the various muscles, they 

 do not interpret the functions of some of these exactly in the same manner, and as a 

 number of names have been applied to designate the same muscle, the first thing to do 

 will be to place before the readers figures showing the position of the impressions and the 

 synonymous terms that have been employed, and these will also save us the necessity of 

 describing the scars, which a glance at the figures will explain far better than could be 

 done by simple words. 



The muscular system is much more complex in the unarticulated divisions of the 

 Brachiopoda than in the articulated groups. While describing their shape and direction 

 we cannot do better than to follow what has been said by Mr. Hancock in his admirable 

 memoir upon the "Anatomy of the Brachiopoda," published in the 'Philosophical Tran- 

 sactions of the Royal Society,' 1S5S : 



The anterior occlnsors " are a pair of stout muscles, of about equal thickness through- 

 out ; they pass from the ventral valve, one at each side, in front of the visceral mass, and 

 inclining forwards and inwards, they go to be attached to the sides of the central ridge 

 of the dorsal valve, about one third of the length of the shell from the anterior margin. 

 The dorsal extremities are compressed, and have their sides in contact." 



The posterior occlusors " are rather stouter and much stronger, and go directly from 

 valve to valve, parallel with each other. The ventral extremities are placed a little in 

 advance of the corresponding terminations of the anterior pair, and the dorsal extremities 

 of the former are situated a little behind those of the latter." 



The divariealor, "though forming a single mass, is really two muscles combined. It 

 is short and stout, and is situated at the posterior extremity of the perivisceral chamber, 

 passing directly between the valves, and Laving its attachments immediately within the 

 umbones. The extremities have a semicircular form, arched behind, and slightly bifid 

 in front, indicating its double nature." 



thanks to the distinguished French anatomist for the high honour he has conferred by dedicating to me 

 the result of his admirable researches. For details concerning the animal of Lingula! must refer the reader 

 to the following memoirs: — Cuvier, ' Memoire sur l'Auimal de la Lingula,' 1797 and 1802. Vogt, ' Ana- 

 tomie der Lingula anatina,' 1845. Owen, "On the Anatomy of the Brachiopoda," ' Trans, of the Zool. 

 Soc.,' 1835 ; as well as in Davidson's 'General Introduction,' chap, i, 1853. S. P. Woodward, 'Manual 

 of the Mollusca,' 1854. But especially to the magnificent memoir by Hancock, " On the Organization of 

 the Brachiopoda," 'Trans. Royal Soc.,' 1858. As well as to Gratiolet's most important and excellent 

 memoir, " Etudes Anatomiques sur la Lingula anatina," in the 'Journal de Conchyliologie,' for January 

 and April, 1860. 



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