PLATE IV— Conlinaed. 



KUTOROIXA. Billing.*. 



Page ao. 

 Kl'tougiva ciNGuiiATA, Billiugs. 



Fig. 10. The pedicle-valve of an exiimiilH with a low, scarcely incurved beak. X -. 



Fig. 11. The brachial valve. X 2. 



Fig. 12. Profile of a pedicle-valve from which the shell i.s larsfcly reiiidved ; sliowiufj the degree of incurv- 

 ature. X 3. 



Fig. 13 A pedicle-valve with a strongly iucurved pubp; drawn, fiiom an internal cast. X 3. 



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



Fi". 15. A brachial valve; drawn from a gutta-'pel*ha impression of a natural mould of the exterior. 

 Natural size. ^ n A 



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

 nuiscnlar ridges near the beak. X 2. '' !^' '. ' '' ' '■■''''''''''' 



Fi". 17. A brachial valve in which the cardinal margin is not transverse, as in the' othei- examjiles fig- 

 ured, but is strongly reentrant. X 2. -"'I. !" I'l 11)111 -I , 



Georgia group. Swanton, Vermont. 



KUTORGINA LaTOUKENSIS, Mill tllCW. 

 Fig. 18. A pedicle-valve ; di-awn from a gutta-pei'cha cast from a natural mould of the extenor. X 6. 

 Fig. 19. Profile of the same. X (i. 



Fig. 20. Cardinal view of the same; showing the open triangulai- fi.ssure. X •'. 

 St. .John g-roiiii. Partland, New Bi-utiswick. 



M E80TR ETA , Kutorga. 



Page 109. 



Mesotreta tkntorium, Kutoi-jra. 



Fig. 21. The pedicle-valve ; copieil fiom Kijtoiwa's \vork, Ueber^die Braehiojjoden-fivnulie der Siphono- 

 treta-a;, pi. vii, fig. 4c. , ' ' . ' 



Lower Silurian. Mussia. 



SIPIIONOTRKTA, Vkunkuil. ' 



i'age 110. 

 SiPIIONOTRETA UNGUICULATA, Vt'lllOllil. 



Fig. 22. Cardinal ])ortion of the pedicle-valve; showing the inner extension of the sipho, which is ajvpar- 



renlly atrophied and ca^cal. ' i ' 

 Fig. 23. A similar portion of anothei- valve in whiih flii. sijiho is open. 



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

 Fig. 24. A portion of the shell near the anterior luaii,^,,, much enlarged to show the tubular strncture, the 

 e])iilermal layers and the mode of origin of the hollow spines. 

 (KuTOKGA, op (ii., pi. vi, tig. 2c.) 

 Figs. 25, 2(5. The intei'ior characteis of I)oth valvesas given by Davidsoit. 

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



SCHIZAMBOX, AA'alcott. 



Page 113. 

 ScniZAMBON TYPICALI.S, AValcott. 



Fig. 27. The interior of a iiedicle-vaUe ; slunving an oval foiamen with the groove or depressed track, and 

 diverging lateial muscular ridges. X 5. 1 



Fig. 2S. The exterior of a brachial valve ; showing the radiating and concentric stiise. In this specimen 

 the surface appears fim^ly granulose, the granulations pi-obaVily lieing the bases of minute 

 spinules like those rei)resonte<l by Mr. Walcoit (Pala'ont. Rui-eka Dist., pi. i, Hg. 3d). 



Fig. 29. The interior of a bi-achial valve ; showing the Outline of the muscular area and its subdivision 

 by diverging ridges. X 5. 



Fig 30. Another interioi- of a brachial valve, differing fi-om the foi'egoing in the less conspii'uons ilivision 

 of the muscular area. The inner |)air of diverging ridges terminate anteriorly in deeply col- 

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



Luwcr jMirtion of llie Pugoiiip group. Eiirikii DixtiUf, Nerada. 



