r.8 



On a 7}ew Alycaeus and a Bulimulus. 



which is very generally met with in the Anaraphideje 

 and is always absent in the Bacilloideje ; it is that the two 

 valves of the sanie tVnstulc do not correspond with respect 

 to the position of thoir pattern or of their processes : for 

 example, the two spots situated on the margin of each of 

 the valves in the genus Actinocrjdus are not sui)erj)osed, but 

 placed in such manner that the two lines which join them to 

 the respective centres form an angle. The same is the case 

 with regard to the protuberances in the genus Aulacodiscus 

 and the awns of the genus Chceioceros. The genera Rhizo- 

 solenia^ Cerataulina, Guinardia, Actinoptychus^ AuliscuSj 

 Asteromphalus, Asterolampraj the majority of species of 

 Biddulphia {cf., for example, B. Smithii), and many others 

 are in the same case. The frustule might be said to be more 

 or loss spirally twisted about its longitudinal axis. 



The new system of classification is shown, then, in the 

 scheme on p. 67. 



The four diagrammatic figures rej)re3ent transverse sections 

 across the frustule of a representative of each of the four 



2. 



Raphidea;. 



Carinatae. 



Mobiles. 



3. 4. 



I 'L „ y J' \y I . J 



Bacilloidetc. Anaraphideae. 



V ,,. / 



Immobiles. 



groups: e. g., Navicula (fig. 1), Nitzschia (fig. 2), Synedra 

 (fig. 3), and Aulacodiscus (fig. 4). They will serve to show 

 the relations existing between the new divisions and sub- 

 divisions of diatoms established in the present note. 



XIV. — Descriptions of a new Alyca2us /rom Perak and a 

 Bulimulus /ro7n Bolivia. By HuGH FULTON. 



AlyccBus con for mis J sp. n. 



Shell very narrowly perforate, conical : apex reddish ; lower 

 whorls sometimes cream, sometimes suffused with ])ale pink, 

 closely and finely obli<|uely striated; nepionic whorls with 

 similar striation, but in reverse direction : whorls 5, very 



