208 T. Davidson — What is a Brachiopod ? 
(Plates VII. and VIII. accompanied Part I. of Mr. Davidson’s memoir ) 
Fig. CLISTENTERATA. PLATE IX. 
1. Waldheimia ßavescens. Interior of ventral valve. /. foramen; d. deltidium; 
t. teeth ; a. adductor muscular impressions ( = occlusor Hancock) close 
valves ; c. divaricator Hancock (= Cardinal muscles King — muscles 
diducteur principaux, Gratiolet) open valves ; c'. accessory divaricators 
Hancock (= muscles diducteurs accessoires Gratiolet ) ; b. ventral adjustors 
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- 
vulär 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 ; l. loop ; v. mouth ; z. extremity of intestine ; 
a. adductor ; c. divaricators; c . accessory divaricators ; b. ventral adjus- 
tors ; b' . peduncular muscle ; b" . dorsal adjustors ; P. peduncle. 
4. Interior of dorsal valve to show the position of the labial or 
brachial appendages; a portion of the fringe of the cirri has heen 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,s. septum; V. mouth. The adjustor or peduncular muscles have 
heen purposely omitted. 
6. Waldheimia ßavescens. Portion of the labial appendages, enlarged, showing 
the interbranchial membrane. w. the canal ; y, q. ciliated cirri coated 
with spicul® (after E. Deslongchamps). 
7. Khynchonetla psittacea. Interior of dorsal valve. a. adductor muscular im- 
pressions ; l. short curved lamellfe for support of labial appendages. 
8. Showing the spirally rolled labial appendages (after Owen’s 
original figure, Trans. Zool. Soc. vol. i. pl. 22, hg. 14) ; but I hnve given 
a more correct illustration of the position of the brachial appendages, of 
K. nigricans, in the Memoirs of the Soc. Linneenne de Normandie, pl. 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. 
TRETENTERATA. 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 ; j, k, l. lateral muscles (j. anteriors, k. middles, l. Out- 
sides), enable the valves to move forward and backward on each other. 
3. 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. 
4. enlarged (after Hancock), to show the dorsal pallial lobe or 
mnntle turned back to expose the pallial chamber; c. marginal fold; r. 
pallial sinuses ; o. spirally coiled brachial apparatus ; e". liver ; l. 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). 
