OF THE TONGUE OP PAEEOTS. 



223 



this stage. The inner portion of the ceratoglossns inferior anticus has retrogressed to 

 stage II. The ceratoglossus inferior posticus extends backwards nearly to the posterior 

 extremity of the hypobranchial, and forwards a little anterior to the hinder margin of 

 the basihyal; posteriorly it gives off a muscular strip (cf/.P.) which passes inwards and 

 forwards to the posterior border of the basihyal and near to the root of the urohyal 

 {cf. Brotygerys, ante p. 221). This little strip is only found on the left-hand side of 

 the tongue ; it is developing a very small tendon at its posterior extremity. 



In Ptistes erythropterus (PL XXVIII. fig. 35) the inner portion of the ceratoglossus 

 inferior anticus has retrogressed to stage II, and the ceratoglossus inferior posticus of 

 the right side is like that in Bolhorhynclms. On the left side it is very different, and 

 the tendon gives origin to two divergently arranged muscles, the outer [cg.i.]).) of which 

 is inserted to the anterior half of the hypobranchial, and the inner (cg.i.a^.) to the 



Text-fia;. 4. 



rezo23orus formosits. — Ventral view of a dissection of the left ceratoglossus inferior posticus to show the 

 division of the muscle. The ventral layer (ceratoglossus inferior posticus ventralis = a) has been removed. 

 (Thrice nat. size.) 



II. 1>. = hj'pobranchial (left side). 



= tendon of ceratoglossus inferior. 



= anterior limit of the insertion of the ventral division of the muscle. 



= median division of the muscle. 



= dorsal division of the muscle. 



urohyal. It thus exhibits the completed stage of that condition which was fore- 

 shadowed in Cacataa leadbeateri {cf. ante, p. 217), and which could be reassumed 

 if the inner portion of the ceratoglossus inferior anticus {cg.i.a^.) were to grow 

 backwards and become confluent with the urohyal portion [cg.i.a-.) of the posterior 

 ceratoglossus. A comparison of the two muscles leaves but little doubt that the 

 urohyal portion (cg.i.a.^) is a portion of the inner part of the ceratoglossus inferior 

 anticus which has separated from that and secondarily become attached at an early 

 stsige to the tendon of the ceratoglossus inferior posticus. The' early stage in this 



