BELEMNITES OF THE LIAS. 



59 



distinctly and definitely, both forward and backward. It is \ inch long. The lateral 

 grooves or flatteuings are variable in distinctness. 



Belemnites striolatus, n. s. PI. X, fig. 25. 



Guard. Compressed, elongate, tapering gradually to an attenuated, conical, finely 

 striated apex ; the strise extend continuously over half the post-alveolar space, and in 

 well-preserved specimens can be traced onward into minute, interrupted, undulated strise, 

 over nearly the whole surface. Where best seen (one third of the post alveolar space from 

 the apex), there are about 100 strise. 



Sections across the guard behind the alveolus are elliptical, the axis but slightly 

 excentric. 



Dimensions. The largest observed is 85 inches long ; of this length | inch is crushed 

 over the alveolus ; greatest diameter (uncrushed) less than 5 inch. The smallest specimen 

 is less than 2 inches in length. 



Proportions. Taking the diameter from back to front at the alveolar apex at 100, 

 the cross diameter is 85, the ventral radius 45 or more, and the dorsal 55 or less; the 

 axis is therefore but little excentric, and measures 500. 



Locality. On the Upper Lias Scars at Saltwick, near Whitby, and in the same beds 

 at Robin Hood's Bay {Phillips). A small number of specimens from the Belemnite-beds 

 under Golden Cap are identified with this species [Phillips). A few small young examples, 

 Glastonbury {Moore). 



Observations. The affinity of this to the last-described species is obvious ; and it is 

 quite possible that further research may unite several of the forms here named separately 

 into one species. But that will not render useless the nomenclature, if it expresses real 

 and often observable peculiarities, for these are elements in the problem of the variation 

 of life-form, in relation to time, space, and physical condition. 



It is doubtful whether this species has been described. Simpson's description of 

 Belemnites substriatus agrees, indeed ; but the fossil is much larger than my specimens, 

 an example in the Whitby Museum being 5J inches long. 



" Similar in general form to Bel. trisulcosus, but with numerous strise at the apex, and 

 no grooves." (Lias Belemnites, No. 16.) 



Belemnites subtenuis of Simpson contains, beside the trisulcose form which is cha- 

 racteristic, two others which are described as varieties, viz. — 



Var. a. Grooves obsolete, apex not striated. 



b. Thicker in proportion, apex not striated. 



This want of striation is the only obstacle which seems to forbid the otherwise 

 probable union of the varieties a and b to B. striolatus. 



