43 GEPHYREA 



confined to the last-named area, which thus again forms the head- 

 quarters of a genus. 



Golfingia, described by Lankester from a single specimen, was 

 dredged in St. Andrews Bay, at the depth of 10 fathoms. 



Petalostoma comprises but one species, P. minutum, which is 

 found in the English Channel. 



Onchnesoma comprises two species, 0. steenstrupii and 0. 

 sarsii, both found off the coast of Norway at considerable depths 

 between 200 and 300 fathoms. 



Tylosoma comprises one species, T. lutkenii, also from the 

 Norwegian coast. It is dredged from stony ground in 50 to 80 

 fathoms. 



II. Order Priapuloidea. 



Anatomy. This Order consists of the two genera Priapulus 

 and Halicryptus. Both are cylindrical animals with the mouth 

 at one end and the anus at the other. The introvert is short, 

 and is covered with rows of chitinous spines, which are con- 

 tinued to some extent over the body. 



The skin is folded in a series of rings, and the body is usually 

 somewhat swollen posteriorly. P. caudatus bears a curious caudal 

 appendage, beset with a number of hollow lobes somewhat grape- 

 like in appearance. This is situated ventral to the anus ; its 

 lumen is continuous with that of the body-cavity, but it can be 

 separated from it by the action of a sphincter muscle. Two such 

 appendages exist in P. bicaudatus. 



There cannot be said to be any head in the Priapuloidea ; they 

 have no tentacles or tentacular fringe, no proboscis, and no 

 distinct brain ; simply a round aperture, the mouth, which is 

 surrounded by a groove in the skin, at the bottom of which 

 the circumoesophageal nerve-cord lies. The mouth leads into a 

 very muscular pharynx lined with stout chitinous teeth ; this 

 passes into an intestine, which is as a rule straight, but in P. 

 ylandifer it has a single loop. 



The Priapuloidea possess no vascular system and no brown 

 tubes. Their skin has in the main the same structure as that of 

 the Sipunculids, with spines, glandular bodies, and papillae with 

 sensory hairs which resemble similar structures on Phymosoma 

 varians. Retractor muscles arise from the longitudinal muscles 



