CLASSIFICATION. 61 



he divides the Ctenobranchiates into two sub-orders : the Pro- 

 boscidifera, which he believes zoophagous, furnished with an 

 entirely retractile trunk, and the Rostrifera. having a contractile, 

 but not retractile, trunk, and sometimes very long, as in Stru- 

 thiolaria, which he supposes phytophagous. 



This author has thus placed the sections of Toxoglossa, Gym- 

 noglossa, Ptenoglossa and Taenioglossa in these two sub-orders. 

 The small value of the retractile trunk as an ordinal character is 

 proved for example in the Bullichv ( Bulla vexillum, possessing a 

 very long retractile trunk). Odostomia has also a very long re- 

 tractile trunk ; and the rather short trunk of Janthina is very 

 often retracted into the head. 



In a more recent work,* Dr. Gray has reunited all the Toxo- 

 glossae in a single division Toxifera, still retaining for the other 

 divisions the separation into two widely removed sections. The 

 name of Ctenoglossa is changed to Ptenoglossa ; the name 

 Trapezodonta is proposed for the Coriocellag, the teeth of which 

 do. not appear to Prof. Morch to differ from the Tsenioglossae 

 except in the want of the two internal teeth on each side (1. 0. 0. 

 1 . 0. 0. 1 ). Heteroglossa is proposed for the Cyclobranchiates. 



In 1854, Morch divided the cephalophora into five great 

 groups, namely : I. Rhipidoglossata (including the Cyclo- 

 branchs) ; II. Ptenoglossata ( Pulmonata, Tectibranchiata, Jan- 

 thinidae) : III. Tsenioglossata (including Pneumonopoma and 

 Heteropoda) ; IV. Hainiglossata (Proboscidea of Troschel, 

 Odontoglossa and Rachiglossa of Gray); V. Toxoglossata (in- 

 cluding Pleurotoma and Terebra). In 1857, Morch reduced the 

 five principal divisions to three, namely : 



I. MusiVOGLOSS AT A (corresponding to the Ptenoglossata of 

 1856, but thus modified because this name has been used by M. 

 Troschel to characterize the group of Janthinne and Scalariae), 

 Pulmonata and Tectibranchia. 



II. ARTHIOGLOSSATA, including : 1. Ttenioglossata, 2. Ancis- 

 troglossata, 3. Toxoglossata. 



III. RHIPIDOGLOSSATA, with the section Orthodonta (Cyclo- 

 branchiates). 



In 1861-2, circumstances having induced Prof. Morch to 

 study the Planarians, he was struck with their great affinity 



* Guide to Brit. Mus., 1857. 



