S9 



Paa Grændsen mellem Hovedet og Nakkesegmeutet 

 ligger de 2 kraftige Kiiidhakker og tæt Iiag dem 

 paa Bngsiden de 2 Par Kjæver. Truiicus bærer 

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

 rende Aiital meget uniforme .Segmenter. Haledelen 

 er Ilden egentlige Lemmer, men bærer paa Spidsen 

 2 stærke, bevægelige Klor og dorsalt 2 smaa jevn- 

 sidesstillede Borster. 



Jeg gaar nu over til at beskrive etlivert af 

 disse Afsnit noget noiere. 



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

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

 iiregelmæssig triangular Form. Dets dorsale Flade 

 er jevnt eonvex og bærer i Midten et eiendommeligt 

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

 mindeligbed er tydet som et Fastlieftningsredskali. 

 Pandedelen er stærkt fremspringende, næsten koniskt 

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

 ken de sammensatte Øine har sin Plads. Nedenfor 

 Pandedelen har Hovedet en dyl> vinkelformig Iiid- 

 liugtning, hvorved Pandedelen meget skarpt sondres 

 fra det triangulært fremspringende Rostrum. Dette 

 sidste er noget trekantet i Gjennemsnit, idet det 

 oventil har en tilskjærpet Kant, 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 liurtigt 

 fortil mod den smalt tilriTudede Pandedel. 



Xakkesegmentet er oventil sondret fra Hovedet 

 ved en meget distinct og temmelig dvb Indbugtning, 

 i hvis Bund der lader sig paavise en tydelig tvær- 

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

 med et lidet stærkt chitiniseret Frems])ring, hvortil 

 Kindbakkernes ovre Ende er articuleret. Den dor- 

 sale Del af Segmentet er stærkt hvælvet og næsten 

 af samme Længde som Hovedet, hvorimod den ven- 

 trale Del er meget kort og kun indskrænket til 

 Mellemrummet mellem Kindliakkei'ue og Skallens 

 Tyukkemuskel. 



Den egentlige Krop (truneus) (seFig. Ij er over 

 doblielt 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 liagerste 

 sædvanligvis er nfuldkomment .sondret. Alle Seg- 

 menter, med Undtagelse af de allerforreste, har 

 oventil et Knippe af bagudkrummede Borster, mest 

 iidviklede paa de bagerste Segmenter. Xogen tyde- 



1'1 — G. 0. Sårs; Fauna Norvegiæ, 



on the under side in the form of the labrum. On 

 tlie boundary between tlie liead and the ceivieal 

 segment lie the 2 powerful mandibles, and immediately 

 Ijeliind them on the ventral side, the 2 pairs of 

 maxilhe. The trunk cai'ries from 22*to 24 pairs of 

 branchial legs, and is divided into a corresponding 

 nunilier of very uniform segments The caudal sec- 

 tion is without any true limbs, but carries at the 

 extremity 2 strong, moval)le claws, and dorsalh- 2 

 small, iuxtaposed l)ristles. 



I will now pass on to describe each (if these 

 sections more fully. 



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

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

 of an irregular, triangular shape. Its dorsal surface 

 is evenly convex, and carries in tlie middle a pecu- 

 liar, stalked, somewliat 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, whereliy the frontal part is ver\- sharjih' 

 divided from the triangularly projecting rostrum. 

 The latter is somewhat triangular in section, having 

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

 lowed out along the middle. The bottom of the 

 groove appears, when the lieail is seen from the 

 side, like a curved line extending from the point of 

 the rostrum l)ackwards towards the base of tlie 

 lalirum. Seen from above .tig. 3) or from below 

 (tig. 4), the head looks ratlier broad at the back, but 

 tapers rapidly in front towards the narro'\\-ly I'ounded 

 frontal part. 



The cervical segment is separated above from 

 the head by a very distinct and ratlier deep hollow, 

 at the Ixittom of which may be traced a dis- 

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

 side in a liighly cliitinised 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, tlie 

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

 and contined only to the space between the man- 

 dibles and the adductor muscle of the .shell. 



The body ])ro]ier (trunk) (see fig. 1) is more 

 than twice as long as the 2 preceding sections 

 together, and almost cylindrical in shape, or only 

 verv 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 the number 

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

 however, the hindmost is generally imperfectly 

 defined. All the segments, with the excejition of 

 the very foremost ones, have a bunch of backward- 

 curved bristles above, those on the hindumst seg- 



