No. 19.] ECHINODERMS OF CONNECTICUT. I3 



CLASSIFICATION 



All the >Echinoderms of the world are divided by zoologists 

 into two sub-phyla, only one of which, the Eleuthe^ozoa, is repre- 

 sented in our local fauna.* 



The, Eleutherozoa are divided into four classes, all of which 

 have i;epresentatives. living in Connecticut waters. 



Qass I. Aster oidea: Starfishes. — The body consists of a 

 central disk which passes without sharp demarcation into five or 

 more symmetrically arranged arms or rays (Plate I). The large 

 mouth occupies: the center of the disk on the ventral^ or oral 

 surface, while the minute anus is situated opposite^ that is, on the 

 aboral side of the disk. The arms are without joints. A deep 

 groove on the oral side of each arm is thickly covered with tube- 

 feet which serve to move the animal from place to place. 



In Long Island Sound occur four species of this class, each 

 of which has five arms. They comprise the common starfish 

 {Asterias forbesi), the northern starfish (Asterias vulgaris), 



• The second sub-phylum^ Pehnatozoa, which iticludesi the Crinoidea,. or Featiher-stars, . 

 is represented in deep water as far north as off the coast of Maine by a species 

 known as- Antedon dentatus, but this has not been recorded from Long Island Sound. 

 Farther south, and; particularly in very deep water, occur other species, including 

 some of the beautiful " sea lilies." 



Explanation of Plate I. Structure of Starfish and Ophiuran. 



Fig. I. Henricia sanguinolenta. Aboral surface of slender-armed speci- 

 men. (Natural size.) 



Fig. z. Same speciea Oral surface of broad-armed specimen. (Natural 

 size.) 



Fig. 3. Same species. Portion of oral surface of disk and one arm, to 

 show mouth, ambulacral grcxjve, with the two rows of tube- 

 feet, and spines. (Five times natural size.) 



Fig. 4.. Asterias forbesi. Small portion of aboral surface, showing the 

 blunt spines surrounded by circles of pedicellarias, and between 

 the spmes the closely-placed conical or tubular branchiae. 

 (Much enlarged.) 



Fig. 5. Ophiura brevispina. Aboral surface. (Natural size.) 



(Figs. I, 2, and S from photographs loaned by the U. S. Fish Commission 

 with permission of Dr. H. L. Qark.) 



