Dr. R. H. Traquair on the Anatomy of Calamoichthys. 115 



the first of the series of well-developed upper ribs, which extend, 

 in the horizontal intermuscular septum, as far back as the ninety- 

 eighth vertebra. But ribs of the lower series are very deficient in 

 development in comparison with those in Polypterus, where the 

 whole series of abdominal vertebrae, except the first, is furnished 

 with those appendages, which posteriorly attain a considerable 

 length. In Calamoichthys, on the other hand, those lower ribs are 

 very minute, and no trace of them was found in advance of the 

 sixtieth vertebra. The number of abdominal vertebrae, in the 

 specimen alluded to, is 100, of caudal 10 — showing the very great 

 proportional elongation of the abdominal and shortening of the 

 caudal region. The vertebral column projects beyond the last 

 caudal vertebra, as a notochordal continuation or "urostyle" 

 concealed among the rays of the caudal fin. The bones sup- 

 porting the fins agree in their general conformation with those 

 in Polypterus, there being, however, a less ossified state of the 

 radius, ulna, and carpus, while the pelvic bones, along with the 

 ventral fins, are completely absent. The first dorsal finlet is 

 placed opposite the forty-ninth vertebra. 



As regards the form and arrangement of the bones of the 

 cranium and face, the most complete correspondence is found 

 with those of Polypterus, a space being found, however, below 

 the preoperculum, which, in various species of Polypterus, is 

 defended by a variable number of bony plates. The suboper- 

 culum is also completely absent. The arrangement of the 

 mucus-canals on the head is similar to that in Polypterus. 



The arrangement of the muscular system corresponds in the 

 two genera. In Calamoichthys, owing to the great increase of 

 the number of vertebrae, the number of transverse segments of 

 the great body-muscle is also much larger. The muscular layer 

 along the belly is very thin. 



Viscera. — The oesophagus dilates into a flask-shaped stomach, 

 which terminates behind in a cul-de-sac. From the interior part 

 of the stomach, and close behind the entrance of the oesophagus, 

 issues the intestine, which passing first slightly forwards, makes 

 almost immediately a turn on itself, and then proceeds straight 

 back to the anus. A small caecal appendage, with the apex di- 

 rected forwards, is seen in connexion with the intestine shortly 

 after its backward flexure; and a little further down, between 

 this and the anus, a spiral valve of about five turns is developed 

 in the interior. The liver was in none of the specimens exa- 

 mined very voluminous, but much elongated, being continued 

 as a narrow stripe the whole length of the abdominal cavity. 

 The gall-bladder is distinct, and opens into the intestine imme- 

 diately after its flexure, and in front of the caecum. 



The heart is conformed as in Polypterus, with muscular bulbus 



