Paa Grændsen mellem Hovedet og Nakkesegmentet 

 ligger de 2 kraftige Kindlmkker og tæt bag dem 

 paa Bngsideii de 2 Par Kjæver. Truncus bærer 

 22 — 24 Par Brancliialfodder og er delt i et tilsva- 

 rende Antal meget miiforme Segmenter. Haledelen 

 er uden egentlige Lemmer, men bærer paa Spidsen 

 2 stærke, bevægelige Klor og dorsalt 2 smaa jevn- 

 sidesstillede Børster. 



Jeg gaar nu over til at beskrive ethvert af 

 disse Afsnit noget noiere. 



Hovedet (se Tab. XV. Fig. 2, 3, 4) er forholds- 

 vis af ringe Størrelse og, seet fra Siden" (Fig. 2), af 

 iiregelmæssig triangular Form. Dets dorsale Flade 

 er jevnt convex og Isærer i Midten et eiendommeligt 

 stilket, noget kolleformigt Appendix (af), som ial- 

 mindelighed er tydet som et Fastheftningsredskab. 

 Pandedelen er stærkt fremspringende, næsten koniskt 

 udtrukket, og ender i en stump Spids, indenfor hvil- 

 ken de sammensatte Øine har sin Plads. Nedenfor 

 Pandedelen har Hovedet en dyb vinkelformig Ind- 

 hugtning, hvorved Pandedelen meget skarpt sondres 

 fra det triangulært fremspringende Rostrum. Dette 

 sidste er noget trekantet i Grjennemsnit, idet det 

 oventil har en tilskjærpetlvant, medens det nedentil 

 er svagt indhulet langs ad Midten. Bunden af Ind- 

 hulingen viser sig, naar Hovedet sees fra Siden, som 

 en buet Linie, der .strækker sig fra Spidsen af Ro- 

 strum bagover mod Basis afOverlæben. Seet oven- 

 fra (Fig. 3) eller nedenfra (Fig. 4), viser Hovedet 

 sig temmelig bredt bagtil, men afsmalnes hurtigt 

 fortil mod den smalt tilrundede Pandedel. 



Nakkesegmentet er oventil sondret fra Hovedet 

 ved en meget distinct og temmelig dyb Indbugtning, 

 i hvis Bund der lader sig paavise en tydelig tvær- 

 gaaende Sutur (se Fig. 3), der ender til hver Side 

 med et lidet stærkt chitiniseret Fremspring, hvortil 

 Kindbakkernes ovre Ende er articuleret. Den dor- 

 sale Del af Segmentet er stærkt livælvet og næsten 

 af samme Længde som Hovedet, hvorimod den ven- 

 trale Del er meget kort og kun indskrænket til 

 Mellemrummet mellem Kindbakkerne og Skallens 

 T;ukkemuskel. 



Den egentlige Ki-op (truneus) (se Fig. 1) er over 

 dobbelt saa lang som de 2 foregaaende Afsnit til- 

 sammen og næsten cylindrisk af Form, eller kun 

 ganske svagt afsmalnende bagtil. Den er delt i en 

 Række meget uniforme Segmenter, hvert bærende et 

 Par Branchialfodder. Antallet af Segmenter er hos 

 fuldvoxne Individer, i Overensstemmelse med Bran- 

 chialfoddernes Tal, 22 — 24, hvoraf dog det bagersfe 

 sædvanligvis er i^fuldkomment sondret. Alle Seg- 

 menter, med Undtagelse af de allerforreste, har 

 oventil et Knippe af bagudkrummede Børster, mest 

 iidviklede paa de bagerste Segmenter. Nogen tyde- 



]2 — G. 0. Sars : Fauna Norvegiæ. 



on the under side in the form of the labram. Ou 

 the boundary between the head and the cervical 

 segment lie the 2 powerful mandibles, and immediately 

 behind thera on the ventral side, the 2 pairs of 

 maxillæ. The trunk carries from 22 to 24 pairs of 

 branchial legs, and is divided into a corresponding 

 member of very viniform segments. The caudal sec- 

 tion is without any true limbs, but carries at the 

 extremity 2 strong, movable claws, and dorsallj^ 2 

 small, iuxtaposed bristles. 



I will now pass on to describe each of these 

 sections more fully. 



The head (see PI. XV, figs. 2, 3, 4) is of com- 

 paratively small size, and, seen from the side (fig. 2), 

 of an irregular, triangular shape. Its dorsal surface 

 is evenly convex, and carries in the middle a pecri- 

 liar, stalked, somewhat club-shaped appendage (af) 

 which is usually interpreted as an organ of attach- 

 ment. The frontal part is very prominent, almost 

 conically drawn out, and ending in a blunt point, 

 within which the compound eyes are situated. Below 

 the frontal part, the head has a deep angular inden- 

 tation, whereby the frontal part is very sharply 

 divided from the triangularly projecting rostrum. 

 The latter is somewhat triangular in section, having 

 above a sharp edge, while below it is slightly hol- 

 loAved out along the middle. The bottom of the 

 groove appears, when the head is seen from the 

 side, like a curved line extending from the point of 

 the rostrum backwards towards the base of the 

 labrum. Seen from above (fig. 3) or from below 

 (fig. 4), the head looks rather broad at the back, but 

 tapers rapidly in front towards the narrowly rounded 

 frontal part. 



The cervical segment is separated above from 

 the head by a ver^^ distinct and rather deep hollow, 

 at the bottom of which may be traced a dis- 

 tinct transverse suture (see fig. 3) ending at each 

 side in a highly chitinised process, to which the 

 upper ends of the mandibles are articulated. The 

 dorsal part of the segment is considerably vaulted, 

 and of almost the same length as the head, the 

 ventral part, on the other hand, being very short, 

 and confined only to the space between the man- 

 dibles and the adductor muscle of the shell. 



The body proper (trunk) (see fig. 1) is more 

 than twice as long as the 2 preceding sections 

 together, and almost cylindrical in shape, or only 

 very slightly tapering behind. It is divided into a 

 series of very uniform segments, each bearing a 

 pair of branchial legs. The number of segments in 

 full-grown individuals corresponds with tlie number 

 of branchial legs, viz from 22 to 24, of whidi, 

 however, the hindmost is generally imperfectly 

 defined. All the segments, with the exception of 

 the very foremost ones, have a bunch of backward- 

 curved bristles above, those on the hindmost seg- 



