CEPHALOPODA. 63 



Cristeltaria sgnammula. — The Scaled Cristellaria. Plate 

 X. fig. 20. Shell externally covered with minute scale-like 

 marks. Fossil. 



Genus 25. RENULINA.— Xamarc^t. 



Generic Character. — Shell kidney-shaped, flat, sulcated, and 

 multiJocular ; volutions linear, contiguous, the second curved, 

 the last lengthened ; the axis marginal. 



Reniilites opercularis. — The Lid- Shaped Renitlina. Plate 

 X. fig. 21. Semilunar, flat, with arcuated concentric ridges. 

 Fossil at Grignon. 



FAMILY VI. LITUOLACEA. 



Shell somewhat spiral ; the last volution continuous in a 

 straight line. 



Genus 26 — IjIT\J Oh K.— Lamarck. 



Generic Character. — Shell multilocular, partially spiral and 

 discoid ; volutions contiguous, the last terminating in a straight 

 line ; chamhers irregular ; septa simple and transverse, the last 

 one perforated with from three to six orifices. 



Lituolites nautiloidea. — The Nautilus- Shaped Lituola. 

 Plate X. fig. 22. Discoid, tailed, ribbed ; septa with six per- 

 forations. Fossil at Mendon. 



Genus 27.— SPIR OL IN A.— Zamarc^i. 



Generic Character. — Shell multilocular, partly spiral and 

 discoid ; volutions contiguous, the last one terminating in a 

 straight line ; septa straight, perforated by a tube. 



Spirolina clavata. — The Club-shaped Spirolina. Plate 

 X . fig. 23. Club-shaped, spiral, smooth, ending in a lengthened 

 erect body. Fossil. 



Genus 28.— SPIRUL A.— Zamarot. 



Generic CAamcfer.— -Shell even, thin, subpellucid, multilocu- 

 lar, spiral, discoid ; the volutions apart with a straight termina- 

 tion ; septa transverse, and equidistant, externally concave, with 

 an interrupted lateral syphon ; aperture round. 



Spirilla Peronii. — Peron's Spirula. Plate X. fig. 24. 

 r2 



