DESCRIPTION OF THE GENERA AND SPECIES. 



NEMERTEA. 



A. PALjEONEMERTEA. 



Family Caeinellida 

 Carinina, n. gen. 



Closely allied to Carinella, from which it differs in the presence of a distinct 

 posterior brain lobe, situated with the rest of the brain and nerve-stems in the integu- 

 ment, outside of the body musculature. A ciliated canal penetrates into this posterior 

 brain lobe. 



Carinina grata, n. sp. (PI. I. figs. 1-3; Pis. II., III., IV.; PI. VI. figs. 1-3; PI. XL 

 figs. 1, 2). 



Two specimens of this new genus and species were obtained in the dredge, both from 

 considerable depths, and from the same part of the Atlantic Ocean, namely, to the east 

 of the United States (Stations 45, 47). The bottom is recorded to be blue mud, and 

 the depth 1240 and 1340 fathoms respectively. This is the greatest depth from which 

 Nemertea have been brought to light, and it is worthy of notice that this deep-sea form, 

 which is at the same time the representative of a new and distinct genus, should be 

 characterised by peculiarities of structure, hereafter to be more fully recorded, which 

 are diametrically opposite to certain of the most striking features of the pelagic genus 

 Pelagonemertes and of other forms that generally occur close to the surface. The most 

 striking of these characters is the exceptionally strong development of muscular tissue 

 in the body-wall, and coincident with this, the considerable reduction of the inter- 

 muscular connective tissue, which in the surface forms becomes a gelatinous matrix in 

 which both the internal organs and the musculature are embedded. 



It can hardly be doubted that this opposite line of development is to a large 

 extent influenced by the much more considerable resistance to be overcome by an animal 

 that has to move about at so great a depth of water. 



Of the external appearance of the fragments of this new species little need be said. 



