﻿208 T. Davidson — What is a Brachiopod ? 



(Plates VII. and VIII. accompanied Part I. of Mr. Davidson's memoir.) 



Fig. CLISTENTEEATA. PLATE IX. 



1. Waldheimia Jlaveseens. Interior of ventral valve. /. foramen ; d. deltidium ; 

 t. teeth ; a. adductor muscular impressions ( = occlusor Hancock) close 

 valves; c. divaricator Hancock (= cardinal muscles King = muscles 

 diducteui' principaux, Gratiolet) open valves ; c'. accessory divaricators 

 Hancock ( = muscles diducteurs accessoires Gratiolet) ; b. ventral adjusters 

 Hancock (= ventral peduncular muscles or muscles du pedoncule paire 

 superieur, Gratiolet) ; b'. peduncular muscle Hancock. 



2. Interior of dorsal valve, c, c. Cardinal process ; b'. hinge-plate ; 



s. dental sockets ; l. loop; a. adductor (=anterior occlusor Hancock; val- 

 vular muscles King ; a. adductor ( = posterior occlusor Hancock) ; c'. ac- 

 cessory divaricator, point of attachment (= muscles diducteurs accessoires 

 Gratiolet; b". dorsal adjustor, points of attachment (= dorsal peduncle 

 muscle = muscles du pedoncule, paire inferieur Gratiolet. 



3. Diagram showing the muscular system after Hancock. M. ven- 

 tral valve ; N. dorsal valve ; I. loop ; v. mouth ; z. extremity of intestine ; 

 a. adductor ; c. divaricators; c'. accessory divaricators ; b. ventral adjus- 

 tors ; b'. peduncular muscle ; b". dorsal adjusters ; P. peduncle. 



Interior of dorsal valve to show the position of the labial or 



brachial appendages ; a portion of the fringe of the cirri has been removed 

 to show the brachial membrane and a portion of the spiral extremities of 

 brachial appendages. 



5. Longitudinal section of valves, with a portion of the animal. 



d, h. labial appendages; a. adductor; c',c'. divaricator muscles ; D. cardinal 

 process; «,s. septum; V. mouth. The adjustor or pedunciilar muscles have 

 been purposely omitted. 



6. Waldheimia Jlaveseens. Portion of the labial appendages, enlarged, showing 



the interbranchial membrane, w. the canal ; y, q. ciliated cirri coated 

 with spiculse (after E. Deslongchamps). 



7. TJiynchonella psittacea. Interior of dorsal valve, a. adductor muscular im- 



pressions ; I. short curved lamellae for support of labial appendages. 



8. Showing the spirally rolled labial appendages (after Owen's 



original figure. Trans. Zool. Soc. vol. i. pi. 22, fig. ] 4) ; but I have given 

 a more correct illustration of the position of the brachial appendages, of 

 R. nigricans, in the Memoirs of the Soc. Linneenne de Normandie, pi. x 

 fig. 11, 1857. 

 9. Terebratella Magellanica. Interior of dorsal valves, to show the double attach- 

 ment of the loop. 

 10. Flatidia anomioides. Interior of dorsal valve, to show the position and shape of 

 the brachial appendages. 



TEETENTERATA. PLATE X. 



1. Lingula anatina. Interior of ventral valve (diagram after King). 



2. Interior of dorsal valve, g. umbonal muscular impressions {open 



valves); h. central muscles {close valves); i. transmedial or sliding muscles ; 

 b. parietal band; /, k, I. lateral muscles (/ anteriors, k. middles, I. out- 

 sides), enable the valves to move forward and backward on each other. 



Diagram of the muscular system (after Hancock). The letters 



indicate the same muscles as are designated in King's figures 1 and 2 ; p. 

 peduncle ; e. heart ; a. alimentary tube ; z. anal aperture. 



enlarged (after Hancock), to show the dorsal pallial lobe or 



mantle turned back to expose the pallial chamber ; c. marginal fold ; v. 

 pallial sinuses ; o. spirally coiled brachial apparatus ; e". liver ; I. lateral 

 muscles ; k. lateral muscles (middles) ; i. transmedial or sliding muscles ; 

 X. lateral wall of body ; z. anal nipple. 



5. Lingula pyramidata (after Morse). Showing manner in which the valves slide 



their valves, also portion of the long peduncle, to which sand has agglu- 

 tinated in the shape of a tube. 



6. Embryos removed from the pallial sinus of Lingula anatina, magnified 120 dia- 



meters, (after Owen). 



