120 PTEROPODA. 



tractile tentacula ; mouth with a retractile proboscis ; two 

 opposite, oblong-ovate, branchiferous wings, connate at their 

 posterior base, being connected by an intermediate lobiform 

 appendage. Shell gelatino-cartilaginous, transparent, and 

 oblong; apex truncated; aperture lateral, anterior. 



Cymbulia Peronii Peron's Cybibulia. Plate XIV. 



fig. 6. Somewhat gelatinous, or cartilagmous; very trans- 

 parent crystalline; oblong, pointed at the vertex, truncated 

 at the base; general shape like a Turkish slipper. Two 

 inches long. Inhabits the Mediterranean. 



Genus 2.— LIMACIN A.— Zamarc^. 



Generic Character. — Body soft, oblong; two branchial 

 fins situated at the base of the neck ; posterior part of the 

 body spiral, and enveloped in a shell. Shell thin, fragile, 

 papyraceous, spiral, with the volutions connected in a dis- 

 coid form. 



Limacina helicialis. — The Helix-like Lijiacina. Plate 

 XIV. fig. 11. Thin, fragile, spiral; the volutions united 

 in a discoid form. Half an inch in diameter. Inhabits the 

 North seas. 



Genus 3.— CLEODORA Peron. 



Generic Character. — Body oblong, gelatinous, contrac- 

 tile ; with a head in front, and two wings ; the posterior 

 part enveloped in a shell ; head distinct, projecting, rounded ; 

 two eyes; mouth in the form of a small beak; destitute of 

 tentacula; two opposite membranaceous, pellucid, and cor- 

 dated wings or fins, placed at the base of the neck. Shell 

 or sheath gelatinoso-cartilaginous, transparent, and in the 

 form of a reversed pyramid. 



Cleodora pyramidata. — The Pyramidal Cleodora. 

 Plate XIV. fig. 9. Pyramidal, triangular; of a gelatinous 

 or cartilaginous substance, very thin and transparent; aper- 

 ture obliquely truncated. Inhabits the American seas. 



