NO. 7 SILICIFIED ORDOVICIAN BRACHIOPODS ROSS AND DUTRO II 



Ulrich and Cooper (1938, pp. 187-191) erected the genus Lept el- 

 Una and presented the first modern description of Leptella, with illus- 

 trations of Leptella sordida (Billings), the type species of Leptella. 

 These illustrations show what seem to be two lobes of a bilobed 

 cardinal process in one specimen. Ulrich and Cooper (1938, pi. 39H, 

 figs. 29, 32, p. 188) interpret these to be chilidial plates. They make 

 no comment on the assignments of any European species to Leptella 

 other than to question their correctness. 



In 1957 Spjeldnaes reclassified many strophomenid genera em- 

 phasizing the importance of the pallial markings. Unfortunately, the 

 vascular arrangements of most North American genera and species 

 are undescribed, unillustrated, or unknown. Spjeldnaes's efforts are 

 commendable but have thrown many of our traditional concepts into 

 disarray. His criteria cannot be applied without considerable revision. 

 In this reclassification Spjeldnaes (1957, p. 66) did nothing with 

 Leptella, but he placed Leptellina in synonymy with Sampo Opik 

 (1957, p. 67-72). However, Sampo possesses a denticulate hinge line 

 by original definition (Opik, 1933, pp. 35-36, pi. 6, fig. 4) . 



Spjeldnaes (1957, p. 70) also assigned the species S. indentata to 

 Sampo, noting that it lacked a denticulate hinge and implying that 

 this important feature is of no consequence (1957, pp. 20-22). We 

 do not have the necessary material at hand to effect the revision of 

 American and European forms that Spjeldnaes' work indicates may 

 be needed. 



Externally these Alaskan shells cannot be classified with Lep- 

 tellina, Sampo, Leptelloidea, or Leptella because the costellation is of 

 more uniform size and even spacing. They lack the prominent car- 

 dinal process of Leptelloidea and Sampo Opik (not Spjeldnaes). 

 They possess a rectangular platform in the notothyrium much like 

 that in Leptella sordida, with only a faint median groove in the pos- 

 terior surface of the platform. A chilidium covers the greater part 

 of this platform. The brachiophores are similar to those of Leptellina, 

 not to those of Leptella. The median septum and circumvisceral flange 

 (brachial lamellae of Opik) are high, narrow, and nearly perpendicu- 

 lar to the plane of the brachial valve, lacking the ragged lamellose 

 appearance found in the other genera above. 



The genus Anoptambonites was described by Williams (1962) 

 covering this very interesting group of shells, and the Alaskan speci- 

 mens fit his descriptions closely. The present occurrence is the first 

 record of the genus in North America. 



Roomusoks (1963, pp. 233-235, pi. 1, figs. 1-4) has included in 



