CRICK : SPECIES OF NAUTILUS EEOM THE INFEEIOK OOLITE. 



123 



nearly one-half of the outer whorl ; aperture not seen, but hyponomic 

 sinus (judging from the direction of the lines of growth) wide and 

 broad. Chambers not very deep, about nine in the last half whorl of 

 the septate part; suture -line with a simple broad shallow sinus on the 

 lateral area, and a broad shallow sinus on the periphery. Siphuncle 

 (in the more inflated form) extra-medial, not seen in the less inflated 

 form. Test varying in thickness, about 1 mm. thick at the edge of 

 the umbilicus, but for the most part much thinner, surface almost 

 smooth, with fine lines of growth which are very faint and almost 

 direct on the lateral area, but are more distinct and form a deep 

 broad sinus on the periphery. In the young shell, up to a diameter 

 of about 16 mm., the test is somewhat coarsely cancellated on the 

 periphery, and the lines of growth relatively coarser and more waved 

 on the lateral area than in the adult shell ; the margins of the 

 periphery are also much less prominent. In the adult there are only 

 very faint longitudinal lines on the periphery. 



Fig. v. — Xaidilus fiiscus, D.sp. a, lateral view of a example oi the less inflated 

 form, showing the suture-lines ; h, peripheral view of the same, showing 

 fragments of the test with its ornaments. Inferior Oolite : Burton Bradstock, 

 Dorset. Drawn from a specimen in the British Museum Collection [C. 4494]. 

 Natural size. 



Dimensions. 



Diameter 



Height of outer whorl 



Height of outer whorl above 



preceding whorl 

 Thickness 

 Width of umbilicus 

 "Width of periphery at 



greatest diameter 



(i) 

 41 

 23 



16- 



29- 

 5 



21 



24*5 mm. 

 13 „ 



9 „ 



(iii) 



53-5 mm. 

 29 



19 



16-5 

 4 



12 



about 33 



7 



about 25 



Remarks. ^-ThxBe specimens in the British Museum Collection are 

 referred to this species : one, No. C. 4494 (iii), is the less inflated form, 



