150 Silurian Fossils of Nova Scotia* 



16. Clidophorus elongatus. N. sp. Fig. 9. 



Shell sub-elliptical, length about twice the height, beaks much 

 nearer to the anterior end, which is narrowly rounded ; umbones 

 rounded, prominent ; a defined gradually widening depression 

 extends from the umbo to the posterior basal margin, causing a 

 straightening or slight sinuosity in the edge of the shell ; a defined 

 ridge along the posterior slope between the sinus and the cardinal 

 margin. Surface very finely striated. A slender clavicle extends 

 from the anterior cardinal margin a little more than half-way to 

 the base, and curving slightly forward. 



This species differs externally from all the others in the greater 

 proportional length and in the rounded umbones. 



The C. cuneatus of the same size is a stronger and proportionally 

 higher shell, having a less defined sinus on the posterior slope, and 

 a much stronger clavicle. 



Fig. 9. 

 1*7. Clidophorus semiradiatus. N. sp. 



Shell somewhat oval-ovate, length about one third greater than 

 the height. 



Surface marked by fine concentric band-like strife, and the 

 posterior slope by flattened dichotomized radiating striae, the two 

 sets of striae gradually dying out at their junction. A faint line 

 anterior to the beak marks the place of the clavicle. 



18. Clidophorus nuculiformis. N. sp. 



Shell nearly equilateral, subventricose, height and length as 

 seven to nine. Anterior end rounded, basal margin regularly 

 curved ; posterior end sub-acute, a slight flattening or depression 

 along the posterior umbonial slope, and between this and the car- 

 dinal line a narrow ridge. On the anterior slope there is a de- 

 pressed line almost parallel to the cardinal line, marking apparently 

 the course of the clavicle. Surface marked by fine concentric 

 striae. 



This species resembles in form the 0. concentricus in its equila- 

 teral form, but the fine unequal concentric striae and the difference 

 in direction of the clavicle are sufficient to distinguish it. 



