576 ORDER PLECTOGNATHI. 



which invests the head and body, so that they have 

 nothing moveable except the tail, the fins, the 

 mouth, and a sort of small lip which furnishes the 

 edge of their gills, all these parts passing through 

 holes in this cuirass. The greater number of 

 their vertebras, also, are cemented together ; their 

 jaws are armed each with ten or a dozen conical 

 teeth. At their gills nothing is seen externally but 

 a cleft furnished with a cutaneous lobe ; but inter- 

 nally, they present an operculum and six rays. The 

 bone of the pelvis is wanting, as well as the ventrals, 

 and there is but a single dorsal and an anal, both 

 small. 



They have but little flesh, but their liver is large, 

 and yields a considerable quantity of oil. Their 

 stomach is membranous and pretty large. Some of 

 them have been suspected of being poisonous. 



They may be divided according to the form of their 

 body, and the spines with which it is armed ; but we 

 are not yet certain that there may not be, in this 

 respect, some differences between the sexes ! . 



1 1. Ostraciones, with triangular body, without spines: Ost. 

 triqueter, Bl. 130. Ost. concatenatus, Bl. 131. 



2. Triangular, armed with spines behind the abdomen : Ost. 

 bicaudalis, Bl. 132. Ost. trigonus, Bl. 135. 



3. Triangular, armed with spines in front, and behind the abdo- 

 men : Ost. qitadricornis, Bl. 1 34. 



4. Triangular, armed with spines on the crests : Ost. stellifer, 

 Schn. 97 ; the same as Ost. bicuspis, Blumenb. Abb. 58. 



[5. With 



