UROCOPTUXE. xi 



treme, the ectocones being reduced or even absent. This 

 genus has perhaps the most highly specialized radula of any 

 Pulmoiiate Gastropod. 



The CENTRAL NERVOUS SYSTEM is in general less concen- 

 trated than in Helicidce, but the data available are too scanty 

 for any general conclusions. Fischer and Crosse have in- 

 vestigated the ganglia of several Mexican forms, and I have 

 figured (xvi, pi. 14) the circumoesophageal ganglia of Bra- 

 ch h ypodella agnesiana. 



The FREE RETRACTOR MUSCLES have been studied in Euca- 

 lodium (pi. 49, f. 16), Cceloccntrwm (pi. 19, f. 43), Holospira 

 (pi. 27, f. 43), Urocoptis (pi. 27, f. 44), and Brachypodella 

 (xvi, pi. 14, f. 3). In Eucalodium the pharyngeal and left 

 retractors branch from the root of the columellar, and then 

 the right ocular, which is thus united a short distance with 

 the columellar. Anteriorly the two ocular retractors join in 

 a muscular plate over the pharynx. In Ccelocentntni the left 

 ocular and pharyngeal retractors are united for a third of 

 their length, and anteriorly the pharyngeal retractor gives 

 off a band to each of them. In Holospira the left ocular is 

 united partway with the pharyngeal, and the right with the 

 columellar muscles. In Urocoptis brevis the muscles arise as 

 in Eucalodium, but are independent distally, and the right 

 ocular functions also as a peuial retractor. Finally, in Bra- 

 cliypodella chemnilziana the pharyngeal and ocular retractor 

 muscles are united for a third of their length, and the colu- 

 mellar or tail-retractor runs free of them. The left ocular 

 retractor (morphologically the right, as this is a sinistral 

 species) gives off a group of fibers to the vas defereus and 

 vagina. It will thus be seen that each of the five genera 

 investigated has a marked individuality in the details of 

 musculature ; but up to this time only about one-third of the 

 genera of the family have been examined in respect to the 

 muscles, and these in only one or two species of each ; so that 

 as yet not much use can be made of the data in phylogenetic 

 studies or systematics. Valuable results will probably follow 

 more extended research. 



The SHELL is always longer than wide, usually more or 



