ECHIURIDA 



315 



opsophageal ring is present which is much elongated, as it extends from 

 the front end of the prostomium to the ventral chord back of the mouth. 

 Special sense organs are wanting but the prostomium acts as a feeler. 



The animals are unisexual, the gonad being unpaired but 



the ducts paired. 



The Echiurida are marine worms which live in the 



sand and mud or between stones, usually near the shore. 



The order contains about 20 species and 5 genera, 3 genera 



and 5 species being known on the Atlantic and 1 species 



on the Pacific coast. 



Key to the genera of Echiurida here described: 



Oj Preanal bristles present 1. Echiukus 



Ca No preanal bristles 2. Thalassema 



Fig. 495 

 Echiurus 



pallasi 



(Wilson). 



1, proboscis 



2, setae. 



1. Echiurus Cuvier. Preanal bristles and 2 ventral 

 hooks present; body marked with rings bearing spines; 

 2 or 3 pairs of nephridia: 3 species. 



E. pallasi Guerin {E. chrysacanthophorus Pourtales) 

 (Fig. 495). Proboscis spoon-shaped but cylindrical at 

 base; about 22 body rings present; color gray, yellow, or 

 orange; length 30 cm. or less; length of proboscis 6 cm.; 

 width 6 cm.: North Atlantic (Casco Bay) and Alaska; 

 Europe. 



2. Thalassema Gaertner. Proboscis rather pointed at 

 end; no preanal bristles but 2 ventral hooks present; 1 to 

 4 pairs of nephridia : 12 species. 



T. melitta Conn (Fig. 496). Color dull red with 8 Ion- ^. ^^^ 



^ =' ^ / Fig. 496 



gitudinal bands; proboscis light yellow; length 25 mm., Thaia,ssema 

 exclusive of proboscis, which is long and flexible: (original) 



drawing by 



Beaufort, N. C, often in sand-dollar shells. H. W. Conn). 



Class 3. HIRUDINEA.* 



Leeches (Fig. 501). Dorso-ventrally flattened, often brightly col- 

 ored annelids, which are completely segmented internally and are marked 

 externally with three or more rings to each somite. A large sucker is 

 present at the hinder and a small one at the forward end by means of 

 which the animal moves on hard surfaces. Parapodia, tentacles, and setae 



* See Leeches of the U. S. Nat. Museum," by J. P. Moore, Proc. U. S. Nat. Mus., 

 Vol. 21, p. 54.3, 1898. "The Hirudinea of Illinois," by J. P. Moore, Bull. 111. St. Lab., 

 Vol. 5, p. 479, 1901. "Notes on the Leeches of Nebraska," by H. B. Ward, Studies 

 from the Zool. Lab. Neb., No. 51. "Hirudinea and Oligochseta Collected in the Great 

 Lake Region," by J. P. Moore, Bull. U. S. Fish. Bur., Vol. 26, p. 155, 1905. "Die 

 Siisswasserfauna Deutschlands, Hirudinea," by L. Johansson, 1909. "The Leeches of 

 Minnesota," by J. P. Moore, Part III, Geog. and Geol. Sur. Minn., 1912. 



