181 CRIBRILINIDJ5. 



clement in the Polyzoan colony the polypide does not 

 ixluhit any differences amongst the Lepralice that can 

 be employed as diagnostic characters in the construc- 

 tion of genera. The avicularian appendages constitute 

 in the present section a very unstable and variable 

 element, and are of very secondary value for syste- 

 matic purposes. In the plan of the gemmation and the 

 colonial habit there is on the whole much uniformity; 

 but the important and difficult question arises, whether 

 forms of kindred zoo3cial character, but exhibiting an 

 erect mode of growth, should be combined in one genus 

 with those which are crustaceous. This and other syste- 

 matic points are discussed in the section of the Introduc- 

 tion devoted to the subject of Classification. 



The present family is a very natural and well-defined 

 group. 



Genus CRIBRILINA, Gray. 



Der. From crilrum, a sieve. 



(,'ELJ.KPORA (part), Fabricius. 



ESCIIARA (part.), Moll. 



LKPUALIA (part.), Johnston : Busk. 



CKIBRILINA, Gray, B.M. Bad. 147 : Snritt, Floridan Bryoz. pt. ii. 



KEPTESCHARELLA, D'Orbigny, Pal. Fran<j. Terr. Cr6t. 



EtciiAinroKA, Srnitt, (Efv. Kongl. Vet.-Ak. Forhandl. 1807, Bihang. 



GENERIC CHARACTER. ZOARIUM incrusting. ZO(ECIA 

 contiguous, having the front more or less occupied by trans- 

 verse or radiating punctured furrows ; orijice semicircu- 

 lar or suborbicular. 



THE peculiar condition of the front of the zocecium, 

 which distinguishes this genus, has a special significance. 

 It is not a mere variety of superficial sculpture, but 



