PLATE IV— Continued. 



KUTORGIXA, Billings. 



Page 90. 

 KUTORGINA CINGULATA, BillillgS. . 



Fig. 10. The pedicle-valve of an example with a low, scai'cely incurved beak. X 2. 



Fig. 11. The bra(thial valve. X 2. 



Fig. 12. Pi-ofile of a pedicle- valve fi'om which the shell i.s largely removed ; showing the degree of incurv- 

 ature. X 3. 



Fig. 13- A iiedicle-valve with a sti-ongly incurved umbo ; drawn from an internal ca,st. X 3. 



Fig. 14. Profile of the same. X 3. 



Fig. 15. A brachial valve; drawn from a gutta-percha impression of a natural mould of the exterior. 

 Natui'al size. 



Fig. 16. The interior of a brachial valve ; showing the radiate ornamentation of the surface and the faint 

 muscular ridges near the beak. X 2. 



Fig. 17. A brachial valve in which the cai'dinal margin is not transverse, as in the other examples fig- 

 ured, but is strongly reentrant. X 2. 



Geoi'gia gi'oup. Swanton, Vennom. 



KuTOEGiNA Latourensis, Matthew. 

 Fi". 18. A pedicle-valve ; drawn from a gutta-percha cast from a natui'al mould of the extei-ior. X 6. 

 Fig. 19. Profile of the same. X 6. 



Fig. 20. Cardinal view of the same; showing the open ti-iangular fiasure. X '5. 

 St. John group. Portland, New Bnmswick. 



MESOTRETA, Kutorga. 



Page 109. 



Mesotreta TENTORIUM, Kutorga. 



Fig. 21. The pedicle-valve ; copied tVom Kutorua's work, Ucdier die Brachiopodeu-familie der Siphono- 

 tret«aj, pi. vii, fig. 4c. 



Lower Silurian. Russia. 



SIPH0N0TRF:TA, Veuneuil. 



Page 110. 



Siphonotreta unguiculata, Yemen il. 



Fig. 22. Cardinal portion of the pedicle-valve ; sho\ving the inner extension of the sipho, whic^ is ajipar- 



reutly atrophied and csecal. 

 Fio-. 23. A similar portion of another valve in which the sipho is open. 



(KuTOKGA, op. cit., pi. vi, fig. 3, a, b.) 

 Fi"'. 24. A portion of the shell near the anterior margin, much enl.irged to show the tubular structui'e, the 

 epidei-mal layei's and the mode of origin of the hollow spines. 

 (Kutorga, op cit.. pi. vi, fig. 2c.) 

 Fig.«. 25, 26. The interior charactei's of both valves as given by Davidson. 

 (Geological Magazine, 1877, pi. ii, figs. 9, 11.) 



SCHIZAMBON, Walcott. 



Page 113. 

 SCHIZAMBON TTPICALIS, Walcott. 



Fig. 27. The interior of a pedicle-valve ; showing an oval foramen with the groove or depressed track, and 

 diverging latei'al muscular lidges. X 5. 



Fig. 28. The exterior of a brachial valve ; showing the radiating .and concentric striae. In this specimen 

 the surface appears finely granulose, the granulations probably being the bases of minute 

 spinules like those represented by Mr. Walcott (Palreont. Eureka Dist., pi. i, fig. 3d). 



Fig. 29. Tlie intei-ior of a brachial valve ; showing the outline of the muscular ai'ea and its subdivision 

 by diverging i-idges. X 5. 



Fig- 30. Another interior of a Ijrachial valve, differing from the foregoing in the less conspicuous divi.sion 

 of the muscular area. The inner pair of diverging ridges terminate anteriorly in deeply col- 

 ored, oval areas, which are too strongly elevated in tlie figure. X 5. 



Luwei- portion of the Pogonip gi-oup. Eamka Bhtrict, Nevada. 



