132 



Selections. 



[No. 7, NEVT SERIES, 



very little known, but seem to distinguish themselves principally 



by their long feelers. Millepora, Retepora. 



2nd. The " Tube-whirlers" (Tubuliporida) which are also of a 

 calcareous nature are nearly free, and only touch the common 

 mass by their extreme end. They are now found in the Southern 

 seas especially, and various genera of this family are to be found 

 in a fossil state from the most remote periods. Tubulipora, Cellu- 

 laria, Crisia, Hornera. 



3rd. The " Crust-whirlers" (Escharida) are easily distinguish- 

 ed from the foregoing families as their round or egg-shaped cells 

 can be completely closed by a moveable covering as soon as the 

 animal is withdrawn. The genera which belong to this family are 

 numerous both in our present seas and in a fossil state. Eschara, 

 Flustra. 



4th. The " Bell-whirlers" {Lagunculida) comprise all those 

 Bryozoa which together with a crown of feelers possess a leather- 

 like cell, and which are generally placed on long stalks on move- 

 able root stocks. Laguncula, Tendra, Bowerbankia, Holodactylus . 



The order of the " Arm-whirlers" (Lophopoda) inhabits fresh 

 water. 



Class Ctenophora. 



The glassy transparent animals of more or less symmetrical form 

 which belong to this class and are to be met with swimming in 

 the sea, have been hitherto classed with the disc and the Tube- 

 medusae in a particular class of Medusas (Acalephae) though be- 

 sides their glassy transparency, they have not a trace of organiza- 

 tion in common with them. 



The " Rib-medusae" (Ctenophora) are generally egg or cucum- 

 ber-shaped, sometimes very broad with a mouth at one end of the 

 body. The organs of motion and the vessels are generally so 

 arranged that they appear like rags to an axis drawn from end to 

 end, while the stomach and ganglious represent the bilateral type. 

 In some the symmetrical type is still clearer as the body is drawn 

 out sideways, even extending itself into a long oblique band in the 

 middle of which the digestive organs are placed. 



The skin of the Rib-medusas is naked, and sometimes, like the 

 Arm-polyps, furnished with holding organs out of which' rises a 



