BRACHIOPODA. 375 



Craniella ulrichi.] 



CRANIELLA? ULKICHI Hall. 



PLATE XXIX, FIGS. 38 and 39. 



1892, July. Craniella ulrichi HALL. Palaeontology of New York, vol. viii, pt. i, pp. 153, 181, 



pi. ivH, flgs. 1, 2. 

 Compare Crania halli SABDESON.* Bulletin of the Minnesota Academy of Natural Sciences, vol. iii, 



p. 328, pi. iv, flgs. 8-10; April, 1892. 



Description: " Shell moderately large. Outline normally circular. Apices sub- 

 central, slightly posterior, inclined backwards. Upper valve with the posterior scars 

 large and the adjustors well defined; anterior scars subdivided, the outer or posterior 

 portion possibly representing the insertion of the brachial muscles. The vascular 

 sinuses make a 3-shaped curve on the lateral portion of the valve, with the crest of 

 the double arch towards the center; narrowing rapidly, becoming indistinct over the 

 anterior region. Lower valve regularly curved, evidently unattached at maturity. 

 Anterior adductors very large, situated on a thickened posterior area. Posterior 

 adductor and adjuster scars very faint, lying just within the margin. The vascular 

 sinuses are a series of low grooves extending forward in subparallel lines from the 

 anterior and lateral margins of the central muscular area. External surface of the 

 valves smooth or covered with concentric sublamellose growth-lines. Length of an 

 upper valve, 16 mm." (Hall, op. cit.) 



The specimens which can be referred to this species are free, separated, strongly 

 convex valves, and are usually overgrown by bryozoans. Associated with them are 

 numerous dorsal valves of Crania setigera Hall, also usually occurring as free valves. 

 These can be separated from Craniella ? ulrichi, when the interior is not shown, only 

 by their outer spinose surface. 



The material of C. ulrichi examined by Prof. Hall is identical with that which 

 we have. All of the attached specimens on which he bases the statement, (p. 153) 

 "is sometimes attached," have proved to be Crania setigera. Among the many 

 specimens of Crania and Craniella observed in Minnesota, not a single attached 

 ventral valve with the dorsal valve removed has been found. When the ventral 

 valve is present it is attached to some other brachiopod and has the dorsal valve 

 covering it. Such specimens have invariably proved to be Crania setigera. That we 

 have both valves among the large and free specimens of Craniella ? ulrichi is prob- 

 able, since the muscular scars and vascular markings are quite different in the two 

 type specimens described and illustrated by professor Hall. This species is, there- 

 fore, biconvex and probably attached by the apical portion of the ventral valve. 



Formation and locality. Eare in the Trenton shales at Minneapolis, St. Paul and near Fountain, 

 in the Galena shales, six miles south of Cannon Falls, Minnesota. 

 Collectors E. O. Ulrich, W. H. Scofleld and C. Schuchert. 

 Mus. Reg. Nos. 7698-7700. 



*Mr. Sardeson's name may really apply to this species, but neither his description nor figures are sufficiently diagnostic 

 to enable us to determine this point satisfactorily. On the other hand, it would seem thathis specimens must be distinct, 

 because he had on several occasions been Informed by one of us that Prof. Hall had named and described the present species 

 In the work above cited. As is well known, part I of that volume was printed nearly two years before it was published. 



