DESCRIPTIONS OF THE SPECIES. - : >< 



HETEROBLASTUS CuMHERLAXDl, sp. llov. 



(PI. VI. figs. 1-G.) 



Sp. (liar. Calyx small, olive-shaped, contracted at both poles; summit small, 

 concave, surrounded by small, projecting, interradial processes ; base small, con- 

 tracted, and concave centrally ; section decagonal ; periphery almost equatorial. 

 Basal plates very small. Radial plates short, forming about one third the length of 

 the calyx, their lateral margins widely divergent ; bodies very small ; limbs with steep 

 sides, obliquely truncated above; lips small, but prominent, ami projecting below 

 the concave base; interradial sutures in slight concavities. Deltoid plates long, 

 lanceolate, nearly two thirds the length of the calyx, and concave in the middle line, 

 produced above the summit into short, sharp, erect processes ; radio-deltoid sutures 

 strongly marked ; radio-deltoid sinuses long, tapering at both ends, the deltoid edges 

 thickened and granulated, the radial edges sharp and plain. Ambulacra subpetaloid 

 below the edges of the sinuses ; lancet-plates apparently exposed in the median line 

 for almost the whole length of the ambulacra ; side plates small, from twenty-five 

 to thirty ; pores piercing the radial and deltoid plates. Hydrospires unknown. 

 Spiracles beneath the projecting apices of the deltoids. Mouth unknown. Column 

 round, composed of slender dice-box-shaped joints. The ornament of the radial 

 plates consists of strong granular lines parallel to the edges ; surface of the deltoids 

 granulo-vermiculate, but with several (usually three) coarse ridges parallel with the 

 radio-deltoid sutures ; deltoid margins of the sinuses with coarse granules. 



Remarks. This exceedingly interesting little Blastoid may be distinguished by its 

 olive-like form, the erect spine-like prolongations of the deltoids, and its small radial 

 plates. In the position of the radio-deltoid sutures it resembles two other British 

 Blastoids, Granatocrinus Derbiensis (PI. IX. figs. 1, 2) and Schizoblastus Rofei 

 (PL VIII. fig. 10). 



We have great pleasure in dedicating this species to the late George Cumberland 

 of Bristol, who was the earliest writer on British Blastoids. 



Locality and Horizon. Gunnerton Burn, near Hexham, Northumberland: 

 Yoredale Shales, Carboniferous Limestone. (Presented by Dr. P. H. Carpenter, 

 F.E.S.) 



Family CODASTERID^, E. & C, 1886. 



Definition. Base usually well developed and sometimes very long. Some or all 

 of the hydrospire-slits pierce the calyx-plates on the sides of the radial sinus, restricted 

 portions of which may remain open as the spiracles. 



Remarks. The four genera which we include in this family present a great diversity 

 of external form, though they have certain very definite morphological characters in 

 common. Cryjjtoschisina Schutzi, Phoenoschisma Yerncuili, Codaster trilobatus, and 



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