216 ZOOLOGY. 
Order 1. Apoda.—The simplest apodous form is the 
Eupyrgus scaber Litken, in which the body shows no 
external signs of longitudinal muscles, though there are 
five small ones, and is covered with spine-like, soft papilla 
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 (Mf, Rinkii Steenstrup) in sand, in shoal- 
water, on the coast of Labrador. A very com- 
mon Labrador Holothurian is Chirodota leve 
Grube (Fig. 153). 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 Synapia, is Leptosynapta Girardit 
(Verrill), our common east coast species, which 
lives in sand at low tide. The body is very 
long, and the animal when disturbed constricts 
its body and breaks up intv several pieces. The 
skin vontains perforated plates and anchor-like 
bodies (Fig. 154). In this genus and those pre- 
viously mentioned, constituting the suborder 
Apneumona and family Synaptide, the sexes 
Fig. 153.—c¢#4- are united in the same individual, and there 
rodotalave. Half . ‘ ‘ 
natural size. @, is no respiratory tree, while the tentacles are 
mouth, closed. simply digitated or lobulated. 
The next suborder, Pneumophora, forming the family 
Molpadide, is characterized by having a respiratory tree. 
In Caudina the skin is rough with calcareous pieces, the 
