602 PHILOSOPHY or ZOOLOGY, 



1). Shell discoid and spiral. 



In this group there are at least four genera, with well 

 marked characters exhibited by the shell. 1. Magiliis, 

 (Montfort). The shell posteriorly is fixed, with regular 

 spires, the last of which is produced into a tube. The 

 animal is unknown. AI. antiquus. The Serpula recta aii- 

 fractibus iribus cont'iguis regulariter involutis, and Ser- 

 pula recta umbilico pervio arifractu apicis unico mvoluto 

 of Walker *, either belong lo this genus, or deserve a se- 

 parate place. 2. Spirorbis. Spires discoid, not produced 

 into a straight tube, and dextral. S. communis, spirilium, 

 granulatus, carinatus, corrugatus and corneas ^ are na- 

 tives. 3. Heterodisca. Like the preceding, but the spires 

 are sinistral. H. heterostrophus, sinistrorsus, minutus, co- 

 nicus, lucidus and reversus, are natives. 4. Lobatula. 

 Discoid, with the tube divided into numerous unequal cells. 

 L. farcta and concamerata, described by Montagu as 

 Serpulse, are native examples. In the genera Serpula, Ver- 

 milia and Spirorbis, the branchiae constitute a tuft of fan- 

 shaped filaments, on each side the mouth. 



2d Tribe. 



Body destitute of a shell. 



A. Branchiae external. 



1. Furnished with antenna. This division includes the 

 Linnean genera Aphrodita and Nereis, now formed in- 

 to numerous genera, which Lamark distributes into the 

 following families. 1. JphrodittK, including Aphrodita •^, 

 Halithea, Palmyia and Polynoe. 2. Nereides, including 

 Lycoris, Nephtys, Glycera, Hesione, Phyllodoce, Syllis, 

 Spio and Diplotis. 3. Eunica; including Leodice, Lysi- 



* Testacca MinuU Rurioia, p. 3. Tab. f. 11, 12. 



■^ The stiuctuie of the aerating organs in this gcnub avc exhibited by 

 Sir E. Home, Phil. Trans. 1815, tab. xiii. 



