DR. T. DAVIDSON OX KECEXT BRACllIOPODA. 



187 



Fig. 20. A. 



(lifTers entirely from tliat of a Limpet. Fuvtliermnre, as observed l)y Dr. Gwyn Jeffreys, 

 " his comparison of the branching- arrangement of the arms to the dusky horns of a wild 

 goat is not inappropriate." 



In 1853 the animal of C. anomcilo was to some extent examined by Dr. S. P. 

 Woodward and myself, and in vol. i. of my ' British Fossil Brachiopoda,' and subsequently 

 in his ' Manual of the Mollusea,' we briefly noticed and figured the thick, fleshy, and 

 spirally coiled labial appendages, directed vertically to the cavity of the dorsal valve and 

 in this respect differing from those we found in Blscina lamellosa; we also observed 

 that the mantle-lobes extend to the edges of the valves and adhere closely, as in 

 Thecidium, their margins being plain and thin. Dr. Gwyn Jeffreys observes, at p. 26 

 of vol. ii. of his ' British Conchology,' that " the animal is by no means timid ; 

 when a camel-hair brush is thrust between the gaping 

 valves, thev immecHatelv close, but in a few seconds after 

 open again, and this teasing experiment can be repeated 

 many times without alarming the Crania or making it 

 sulky. The cirri are not contractile, and do not withdraw 

 or shrink when touched. Each arm has about sixty of 

 them. The fry are quite white and semitransparent, 

 and they have only a few tubular perforations. They 

 adhere in the same way as their jiavents." 



Lucas Bari'ett, who had seen many specimens of C 

 anomala in life between Drontheim and Tromsoe attached 

 to stones and shells, in iO to 150 fathoms water, stated, in 

 the Annals and Mag. Nat. Hist, for 1855 (vol. xvi.), that the 

 cirri, but not the arms, are protruded beyond the margin 

 of the shell. The valves open by moving upon the straight 

 side as on a hinge without sliding the valves — conse- 

 quently no sliding-muscles were required. At my request 

 in 1859 Mr. A. Hancock examined the animal of C. 

 anomala, and in sending me the sketches here reproduced 

 he said " oc are undoubtedly the occlusor muscles, cU the 

 dlcaricators ; when the former relax, and the latter contract, 

 the fluid in the perivisceral chamber will be forced forward, 

 and then the valves will ha opened a little in front. The 

 action is the same as in Lingula ; va may be called the 

 ventral acljitsfors, they form a scar close to the outer 

 border of the divaricators in the ventral valve. The other 

 extremities of the muscles converge and pass rovmd the 

 outer margin of the occlusors to which they adhere ; but, 

 be adds, I could not determine exactly how they terminate. 

 I presume that the other extremities form, as stated, a scar 

 in the ventral valve of C. anomala from the fact of such a 

 scar existing in the fossil Crania ignahergensis. Both the 

 dorsal adjustors, da, and the ventral adjustors, va, are much 



A. Dorsal surfece of an animal of 

 Crania anomala (after Hancock). 



mm, mesenteric muscle ; dl. divari- 

 cators ; da, dorsal adjustors ; va, 

 ventral adjustors ; oc, occlusor : 

 Jjn, brachial muscles; ?<ji>, brachial 

 process. 



B. 



B. Ventral surface of animal of 

 Crania anomala (after Hancock). 



mm, mesenteric muscle ; ac, ali- 

 mentary canal : di, divaricators ; 

 da. dorsal adjustors ; va, ventral 

 adjustors : oc, occlusor ; hm, 

 brachial muscles; h^, brachial 

 process. 



