CLARK: THE STARFISHES OF THE GENUS 1IELIASTER. 



57 



diameter, with 13 and 14 rays respectively. Another specimen of the 

 same species from Guaymas, Mexico (U. S. N. M. No. 21949) is also 25 

 mm. in diameter but has 15 rays. A larger one (110 mm.) from the same 

 place (U. S. N. M. No. 21941) has only 17 rays, of which two are very 

 small ; hut this specimen like the individual of multiradiatus referred to 

 on p. 48, which, although 200 mm. in diameter, has only 16 rays, is al- 

 most certainly the victim of an unusual accident. A specimen of kubiniji 

 C4 mm. in diameter, from Acapulco, Mexico, (M. C. Z., No. 1171), has 

 only 18 rays. I have neither seen, nor found a record of, a specimen of 

 any species with 19 rays. The largest specimen of canopus, 120 mm. in 



\<\ 2o Al 22 23 2* 25 26 zi 2g z? JO 3/ 3Z 33 3¥- J5 34 3/ 3% 31 *A fl 



Diagram 1 L 



To show the relative abundance (per thousand, regardless of species) of Heliasters with 

 20-40 rays. Based on 335 individuals. 



diameter, and the smallest of polybrachius, 40 mm., have only 20 rays 

 each. Ahove 20, all numbers occur up to 44, but I have seen no speci- 

 imen with 41. There are eight specimens with 40 rays each (five of 

 polybrachius, one of cumiwjii, one of microbraehius, one of heliauthus) ; 

 one polybrachius has 42, one polybrachius has 43, and one microbraehius, 

 only 140 mm. in diameter, has 44. The number of specimens with from 

 20 to 40 rays inclusive is 335 and Diagram 1, based on this series, shows 

 the number of individuals in a thousand having any given number of 

 rays between 19 and 41. 



A single glance at this diagram shows that there are two groups of He- 

 liasters, one of which tends to have 23-25 rays, and the other 35, and 



1 In this and all the following diagrams : Horizontal lines show the number of 

 individuals. Vertical lines show the number of rays. 



