184 Introduction to Animal Morphology. 



lanus has two apical shell-like valves based on a chitinous 

 ring, sending off processes. Lecanocephalus has a patelli- 

 form head, a spinulose body, and a sword-like penis-sheath. 

 Heterocheilus, of the Manatee, has a short neck and three 

 unequal lips. Conocephalus, of the Dolphin, has a conical 

 head with a retractile border, a simple uterus, and two 

 ovaries. In Ancyranthus, of the Tortoise, the head is armed 

 with 4-8 pinnatifid spines, with two long central and two 

 small lateral, bicuspid spines ; in Elaphocephalus, found in the 

 sheath of the digital tendons of a macaw, and in Aspido- 

 cephalus, the head has lateral leathery shields and a central 

 mouth. 2. Cirrhostomidae free, thread-like; mouth cir- 

 riferous ; a caudal gland opening at the tip of the often papil- 

 lary, bifid tail ; stomach not globular. Phanoglene has two 

 large cervical eyes. Enchelidium has one postoral pigment 

 mass, with several lenses. The tail has no papilla in the 

 marine Pontonema ; it is suctorial in the freshwater Amblyura. 

 Oncholaimus has two or three, and Odontobius has 3-6 teeth. 

 Knoplus has 2-4 teeth and redeyr->j><-cks. 3. Anguillulidae 

 stomach muscular ; pharynx seldom with chitinous teeth ; no 

 caudal inland. Dorylaimus has a central stilet-like tooth in 

 its protrusible proboscis. Diplogaster has several teeth, as 

 lias Rhabditis, the vinegar and paste eel. Anguillula free 

 or parasitic ; has no teeth nor penial sheath. Myoryctes 

 is parasitic in the muscles of frogs. Pelodytes is her- 

 maphrodite (in Mollusca). Angiostomum has chitinous, 

 pharyngeal plates, and no stomach. Leptodera is bila- 

 biate, and has, like the last, a two-bladed penial sheath. 

 4. Hedruridae mouth two-lipped ; the straight females 

 have a hinder sucking groove with a central hook ; the 

 males are coiled ; penial sheath, none (Hedruris), or 

 double (Symplecta). 5. Ophistomidae mouth two-lipped, 

 ventral ; head cup-like (Stelmius), or rounded, continuous 

 with the body ; sometimes with a chitinous support (Dacnitis) ; 

 female tail unicoronate (Ophiostomum), or bifid (Rictularia). 

 6. Spiruridae long, with terminal mouth ; head papillose or 

 lipped ; hinder end of male coiled, winged (papillose in 

 Eucamptus) mouth, with one papillose, circular (Spirura), or 

 two lips (Cheilospirula), or none (Spiroptera) ; S. hominis 



