134 



ZOOLOGY. 



Order 1. Apoda. — The simplest apodous form is the 

 Uupyrgus scaler Liitken, in which the body shows no 

 external signs of longitudinal muscles, though there are 

 five small ones, and is covered with spine-like, soft papillae 

 bearing calcareous plates. We have dredged it 

 frequently on the coast of Labrador in shoal- 

 water. It has a circle of fifteen unbranched 

 tentacles, and is about one centimetre long. 

 It also occurs in Greenland and Norwegian 

 waters. Myriotrochus has a transparent skin 

 dotted with minute white spots, which, when 

 magnified, appear to be wheel-like, calcareous 

 plates. It has a single Polian vesicle, and there 

 is no respiratory tree nor Cuvierian appendages 

 (Huxley). We have dredged this beautiful 

 form {M. Rinhii Steenstrup) in sand, in shoal- 

 water, on the coast of Labrador. A very com- 

 mon Labrador Holothurian is Ohirodota Icsve 

 Grube (Fig. 90). It lives in shallow, sandy, 

 retired bays, and is whitish-gray, with five dis- 

 tinct muscular bands and scattered white spots, 

 which are calcareous, wheel-like bodies situated 

 in the skin. 



Near Synapta, is Leptosynapta Girardii 

 (Verrill), our common east coast species, which 

 II ll o lives in sand at low tide. The body is very 

 long, and the animal when disturbed constricts 

 its body and breaks up into several pieces. The 

 skin contains perforated plates and anchor-like 

 bodies (Fig. 91). In this genus and those pre- 

 viously mentioned, constituting the suborder 

 Apneumona and family Synaptidm, the sexes 

 are united in the same individual, and there 

 is no respiratory tree, while the tentacles are 

 simply digitated or lobulated. 

 suborder, Pneumophora, forming the family 

 is characterized by having a respiratory tree. 

 In Caudina the skin is rough with calcareous pieces, the 



rodotalcuve. Half 

 natural size, a, 

 mouth, closed. 



The next 

 Molpadidw, 



