654 CAMBRIAN BRACHIOPODA. 



The variation in the strength and number of ribs is from a shght trace of one or two short 

 ribs near the front margin to twenty or more ribs. One extreme is represented (PL LXI) by 

 figure 4a, and the other by figure 4. The specimens illustrated are from the same layer of 

 rock. A. matihewi multicostata Matthew is similar to A. prima costata in surface characters 

 and the presence of radiating ribs, bu- it differs in the more anterior position of the apex on 

 the ventral valve. 



The variety costata occurs in association Avith A. prima and is distinguished from it by 

 the presence of more or less distinctly indicated ribs. 



Formation and locality. — Middle Cambrian; (21i) Sandstones of Division lh2;'^ (301d [Mattliew, 1895a, p. 128]) 

 sandstones of Division IbS;'^ (2i) sandstones of Division lb3; and (2k) just above 2i, in the sandstones of Division 

 lb3; all in Matthew's [1895a, p. 108] Protolenus zone, Hanford Brook, St. John County, New Brunswick. 



(3011 [Matthew, 1895a, p. 128]) Sandstones of Division Id at Porters Brook, St. John County; and (301f [Matthew, 

 1895a, p. 128]) sandstones of Division lb5 of Matthew's Protolenus zone, at Catons Island, Long Reach, St. John 

 River, Kings County; all in New Brunswick. 



(6n) Shales near the top of No. 6 of the Manuels Brook section [Walcott, 1891b, p. 261], Manuals Brook, Concep- 

 tion Bay, Newfoundland. 



AcROTHELE PKiMiEVA (de Vcmeuil and Barrande). 

 Plate LVII, figure 6. 



Discina (Orbicula) primseva de Verneuil and Barrande, 1860, Bull. Soc. g^ol. France for 1859-60, 2d ser., vol. 17, 

 p. 532, PI. VIII, figs. 2 and 2a. (Described and discussed in French as a new species. Figs. 2 and 2a are 

 reproduced in tliis monograph, PI. LVII, figs. 6 and 6', respectively.) 



Acrothele primxva (de Verneuil and Barrande), Pompeckj, 1896, Jahrb. K.-k. geol. Reichsanstalt for 1895, Bd. 45, 

 Hft. 3, p. 603. (Discussed in German.) 



This species appears to have been represented by only the ventral valve; tliis, the authors 

 state, is corneous, slightly convex, and ornamented by very fine concentric striae, and tliree 

 fine lines that radiate from the apex to the front margin. On the figure the apex is about one- 

 third the distance from the posterior to the anterior margin, and a faint false area is indicated 

 by lines that diverge from the apex to the posterior margin. 



As far as can be determined from the illustrations and descriptions of the two species, 

 this form is most nearly related to Acrothele quadrilineata Pompeckj. 



Formation and locality. — Middle Cambrian: (350 [de Verneuil and Barrande, 1860, p. 538]) Red limestone 

 of the Paradoxides zone, near Adrados, north of Sabero and Bonar, Cantabrian Mountains, Province of Leon, north- 

 western Spain. 



Acrothele proles Matthew. 



V 



Plate LXII, figures 3, 3a-e, 4, 4a. 



Acrothele proles Matthew, 1902, Bull. Nat. Hist. Soc. New Brunswick, vol. 4, pt. 5, No. 20, pp. 400-401, PI. XVII, 

 figs. 3a-e. (Described and discussed as a new species. The specimen represented by fig. 3a is redra-i?n in 

 this monograph, PI. LXII, fig. 4. Fig. 4a is drawn from one of Matthew's (unfigured?) specimens.) 



Acrothele proles Matthew, 1903, Geol. Survey Canada, Rept. Cambrian Rocks Cape Breton, p. 60. (Notes on 

 orientation.) 



Acrothele proles Matthew, 1903, idem, pp. 102-103, PI. V, figs. 3ar-e. (Description and figures copied from Matthew, 

 1902a, pp. 400-401, PI. XVII, figs. 3a-e.) 



The most essential difference between this species and AcrotTiele avia Matthew is in the 

 position of the apex of the ventral valve. There are certain minor differences in the visceral 

 callosity, but these are variable and depend more or less upon the state of preservation of 

 the shell. Nearly all the shells of AcrotTiele from the shales and arenaceous beds of the Nova 

 Scotia localities have been distorted by flattening or lateral movement; on this account when 

 one has but a few specimens it is difficult to place confidence on characters subject to change 

 by very slight distortion of the shell. 



f On the doscription of Plate V [Matthew, lS95aJ Matthew says that the type specimen is from divisions lb2 and IbS; there is but one type 

 specimen and it can not be ascertained to which of the two divisions it should be assigned. The specimens in the United States National 

 Museum collections from Locality 2h were collected later than the time at which Matthew made his collections. 



