BRACHIOPODA. 



147 



division by some authors. King* proposed to limit the term Crania to such 

 species as are attached by the uniboiuil portion of the lower valve, e.g., C. Igna- 

 bergensis, and to apply the name Criopus, which had been proposed by Poli in 

 1791 {be. cit.) for the animal of Crania and some other brachiopods, to species 

 attached by the entire surface of this valve. It is a well known fact that many 

 species of Crania were quite unattached during their mature life, and other 

 species are known to have been either attached or free. It therefore appears 

 injudicious to ascribe a high value to so variable a character as the degree of 

 attachment of the lower valve. 



Among Cranias generally there is a more or less distinctly developed tend- 

 ency to the formation of a transverse posterior or cardinal margin, a feature 

 reaching an extreme in Waagen's genus, Cardinocrania. 



It is not usual to find among palaeozoic species any indication of more than 

 two pairs of muscular impressions, the posterior being divaricators and the 

 anterior, occlusors or adductors. The other small muscular bands rarely leave 

 discernible scars, but their position may be learned from the accompanying 

 figures of Crania anomala, Midler, reproduced from Dr. Davidson's Monograph 

 of Recent Brachiopoda,! and made from sketches by Mr. Albany Hancock. 



Crania anomala. After Hancock. 

 FIG 66. Dorsal surface of the a..ira.-,l. Fig. 67. Ventral surface, 



mm mesenteric muscle; <ii, divaricators; da, dorsal aUjustors; ra, ventral adjustors; oc, occlusors; tm brachia 

 muscles; bp, brachial process; oc, alimeutary canal (According to Joubin, this organ should have a median, not 

 lateral termination). 



In addition to the large muscular bands are three pairs of smaller ones ; da, 

 va, the dorsal and ventral adjustors respectively, and bm the brachial muscles, 



* Monograph of the Pei-mian Fo.^sils of England, p. 84. 1849. 

 t Trans. Liiinean Soc. London, vol. iv, pt. 3, p. 187. 1888. 



