62 DE. T. DAVIDSON ON RECENT BRACHIOPODA. 



Mocandrevia cranium, King, Proc. Dublin Univ. Zool. and Bot. Assoc, vol. i. p. 261, 1859. 



Terebratula {Waldheinda) cranium, Reeve, Concli. Icon., Monogr. of Terebratula, pi. iii. fig. 6, 1860. 



Te^'ebratula cranium, Jefi'reySj Brit. Conch, vol. ii. p. 11, and vol. v. p. 163, pi. xix. fig. I, 1863. 



Waldheimia euthyra, Seguenza, Pal. Mai. Class. Brach. p. 46, pi. v. figs. 6-14, 1865. 



Waldheimia cranium, Dall, Am. Journ. of Conch, vol. vi. p. 110, 1870; Friele, Yidensk. Selsk. 

 Forhandl. pi. i. fig. 1, 1875, and Archiv for Mathematik og Natnrvidenskab, pi. i. figs. 1-4, pi. ii. 

 figs. 5-7, pi. iii. figs. 1-4 and 7, 1877 ; G. O. Sars, Mollusca Region. Arct. Norveg. (Christiania) p. 10, 

 tab. i. fig. 3, 1878; Jeffreys, Proc. Zool. Soc. 1878, p. 405. 



Macandrevia cranium, Douville, Bull. Soc. Geol. de France, 3'' ser. vol. vii., 1879; K. A. Zittel, 

 Handb. der Palaontologie, p. 703, 1880 ; E. Dcslongchamps, Etudes critiques sur les Brachiopodes, 

 pi. xiii. figs. 13-16, pi. xiv. figs. 4-9, and pi. xv. fig. 5, 1884. 



Shell lenticular or ovate globose, longer than Avide, broadest about the middle, lateral 

 margins rounded, antex'iorly subquadrate or rounded, sometimes much thickened at the 

 margins. Dorsal valve evenly convex, without fold or sinus. Ventral valve deeper than 

 the dorsal and evenly convex ; beak slightly incurved, short, and truncated by an in- 

 complete circular foramen, margined anteriorly by the umbo and by two rudimentary 

 deltidial plates, which are in many specimens absent ; beak-ridges not very sharply 

 defined. Surface smooth, marked only by concentric lines of growth. Colour yellowish 

 white or light horny. Shell-perforations separated by interspaces of about equal size. 

 Dimensions variable — length 1 inch 1 line, width 10 lines, depth 7 lines. In the interior of 

 the dorsal valve there is no defined cardinal process or mesial septum, but two deviating 

 septa commence under the extremity of the umbo and extend to a little more than 

 one fourth of the length of the valve ; loop long, attached to the base of the hinge- 

 plate, and extending to about four fifths of the length of the valve before becoming 

 reflected *. In the interior of the ventral valve the teeth are supported by strong 

 dental plates. 



Hah- W. cranium is an abundant shell near the coast of Norway and in the northern 

 seas. It was dredged on several occasions by R. MacAndrew and L. Barrett between 

 Vigten Islands and the North Cape, in 25 to IGO fathoms, attached to stones; only abun- 

 dant at Omnsesoe. Dr. Gwyn Jeffreys dredged it many times during the ' Lightning' 

 and 'Porcupine ' Expeditions off the Faeroe Islands, in 161 and 208 fathoms, and as deep 

 as 690 fathoms during the ' Porcupine ' cruise in 1869. MacAndrew obtained it outside 

 Vigo Bay in 30 fathoms, Vl'allich in Greenland, and the Marquis de Polin and Dr. 



* So delicate and brittle is the loop at the point where the primaiy lamellte become reflected, that both Dr. J. 

 (fwyu Jeffreys and Dr. W. B. Carpenter for some time entertained the mistaken opinion that at that point they were 

 naturally disunited. This led Dr. Jeffreys to remark on p. 13 of the second volume of his ' British Conchology ' : — 

 '• Having carefully cleaned the inside of a specimen of T. cranium, containing the dried remains of the animal, with 

 a weak solatiou of potash, and examined several other perfect shells of different ages, I could not perceive the least 

 ajtpearance of a loop, which is so evident in 7'. austraJix. The lamellar processes in the lower valve of T. cranitim 

 are eijual in length, and end in sharp points. They may be compared to the chariot-blades used by the ancient 

 Sevthiaus, and they somewhat resemble the falcifonu apophyses of Teredo and Pliolds. In the young of T. craminn 

 these processes are extremely short. Their airaugcment and .shape are so dissimilar in species closely allied in other 

 respects, that I should be inclined to consider their importance, as characters of generic distinction, somewhat 

 doubtful.'' It was some considerable time before I could convince my distinguished friend that the loop of Wcdd- 

 heimia cranium differed hut little from that of W. Jlavcscens. 



