of the North Atlantie and of North-Western Europe. 667 



A single specimen dredged by the " Talisman," August 11, 1883, off Arcachon 

 in the Bay of Biscay in 2794 metres ; and another in 2333 mfetres, off the coast 

 of Soudan, July 15th, 1883 (Marquis de Folin). 



Genus Teteagonodon,* n. g. 



Shell of ? very tumid, without counting the extremities ovate; rostral 

 process very long, projected almost directly forwards ; greatest height of valves 

 anterior ; hinder extremity triangularly produced infero-posteally, slightly concave 

 above. Antennules of ? six-jointed, third joint shortest ; no sensory appendage. 

 Antennae with setae short, not plumose ; appendicular branch minute, consisting of 

 a single joint terminated with a seta. Mandible with a masticating process cleft 

 only at the extremity ; no fixed spines on basal joint of palp, a small laminar 

 appendage at extremity of that joint, ungues two, rather long. Second 

 maxillse with the three anterior lobes closely pressed together, ending in few 

 setee ; upper tooth of great size, subquadrate, broadly truncate at the end, and 

 smooth-edged ; no lobe or setse beyond the tooth, except those belonging to 

 the three-lobed palp ; vibratory plate well developed. Penultimate limb, as usual 

 four-lobed. Caudal laminae, with the ungues spined on the edge. 



1. Tetragonodon ctenorhynch.us, n. sp. 



• (Plate Lvm., figs. 1-8.) 



General form of shell of female, ovate, excessively tumid, so that the breadth 

 nearly equals the height ; slightly concave on the upper part of the posterior 

 margin, and with a long pointed, nearly erect rostrate process in front ; greatest 

 height equal to four-sevenths of the length, and situated just in front of the 

 middle, from which point the outline declines gradually backwards ; ventral margin 

 from the bottom of the antennal sinus projected boldly outwards, and forming a 

 very convex sweep for two-thirds of the length, behind this it gradually slopes 

 upwards to the hinder extremity ; the dorsal margin passes from the extremity of 

 the porrected rostral process vn.th moderately convex arcuation backwards to 

 about one-half the length of the valve, behind this point the arcuation is only 

 slight, until on reaching the commencement of the hinder margin, it sweeps 

 down obliquely and with slight concavity to the point where it meets the ventral 

 margin and with it forms a blunt angle at the infero-anteal corner. In front 

 the rostral process is of remarkable length, and running out to a sharp point, is 

 projected forwards, an 1 only slightly downwards ; beneath it the antennal sinus 

 lies very widely open ; the surface of the valves is everywhere pitted with little 



* TETpaycovos, square ; oSuii', a tooth. 



