s9 



Paa Grrændsen mellem Hovedet op; Nakke.segmentet 

 ligger de 2 kraftige Kindbakker og tæt Ijag dem 

 paa Bugsiden de 2 Par Kjæver. Tnineus lian-er 

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

 rende Aiital meget uniforme Segmenter. Haledelen 

 er uden egentlige Lemmer, men bærer paa Spidsen 

 2 stærke, bevægelige Klor og dorsalt 2 sniaa jevn- 

 sidesstillede Borster. 



deg gaar nu over til at Ijeskrive ctlivei't a f 

 disse Afsnit noget uoiei-e. 



Hovedet (se Tab. XV. Fig. 2, 8, 4) er forholds- 

 vis af ringe Storrelse og, seet fra 8iden (Fig. 2\ a f 

 uregelmæssig triangular Form. Dets dorsale Flade 

 er jevnt convex og ba-rer i ilidten et eiendommeligt 

 stilket, noget kolleformigt A])pendix (af), som ial- 

 mindelighed er tydet som et Fastlieftningsred.skab. 

 Pandedelen er stærkt frems]ii'ingende, na^steii koniskt 

 iidtrukket, og ender i en stumj) Sjiids. indentnr hvil- 

 ken de sammensatte Oine har sin IMads. Nedenfor 

 Pandedelen har Hovedet en dyb vinkelformig Ind- 

 bugtning, hvorved Pandedelen meget skarjit sondres 

 fra det triangulært fremspringende Rostrum. Dette 

 sid.ste er noget ti'ekantet i (TJennemsnit, idet det 

 oventil har en tilskjærpet Kant, medens det nedentil 

 er svagt indhulet langs ad Midten. Bunden af Ind- 

 liulingen viser sig, naar Hovedet sees fra Siden, som 

 en buet Linie, der strækker sig fra Spidsen af Po- 

 strum bagover mod Basis af Overlæben. Seet oven- 

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

 sig temmelig bredt bagtil, men afsmalnes linrtigt 

 fortil mod den smalt tilrundede T*ande(h'l. 



Xakkesegmentet er oventil sondret fra Hovedet 

 ved en meget distinct (jg temmelig dyb Iiulbugtning, 

 i livis Bund der lader sig ])aavise en tydelig tvær- 

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

 med et lidet stankt chitiniseret Fremsjiring, hvortil 

 Kiiidbakkei'nes ovre Ende er articulcret. 1 )en dor- 

 sale l)el af Segmentet er sta'i'kt hvadvet og na'sten 

 af samme Længde som Hovedet, bvoi-imod den ven- 

 trale Del er meget kort og kun indskra-nket til 

 Mellemrumiiiet mellem Kiiidliakkernc og Skallens 

 Ijukkemuskel. 



Den egentlige Kr<i]i itruncus' srl'"ig. 1) er over 

 dobbelt saa lang som de 2 foregaaende Afsiiit til- 

 sammen og næsten (ylindrisk af Form. eller kun 

 ganske svagt afsmalnende bagtil. Den ci- delt i en 

 Pække meget unitV)rnu' Segmenter, hvert lueri'ude et 

 Par Branchialfodder. Antallet af Segmenter er hos 

 fuldvoxne Individer, i ( Keiensstemmelse med Bran- 

 chiali'oddernes Tal, 22 — 24, hvoraf dog det bagerste 

 sa>dvanligvis er ufuldkomnu'ut sondret. Alle Seg- 

 menter, med llndtagelse af de allerforreste, har 

 oventil et Knippe af bagudkrunuuede iiorster, mest 

 udviklede paa de bagerste Segmenter. Xogen tyde- 



]'2 — G. O. S.-ws : Fonna yon-eptx- 



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

 tiie boundary between the head and the cervical 

 segment lie the 2 powerful mandibles, and immediately 

 behind them on the ventral side, the 2 pairs of 

 nmxillæ. The trunk carries from 22 to 24 pairs of 

 branchial legs, and is divided into a corre.sponding 

 niunber of very uniform segments. The caudal sec- 

 tion is witiiout anv true limbs, but carries at the 



extremity 2 strong, movable claw: 



d ilorsal 



snmll, iuxtajjosed bristles. 



I will now ]iass on to describe eaidi of these 

 sections more i'ully. 



The head (see PI. XV, tigs. 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 pecu- 

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

 which is usually interpreted as an organ of attach- 

 nu'ut. The frontal ])art is very ])rominent, almost 

 conically drawn out, and ending in a blunt point, 

 within which the comjiound eyes are situated. Below 

 the frontal ])art, the head has a dcej) angular inden- 

 tation, whereby the frontal part is very shar])ly 

 divided liMim the triangularly projecting rostrum. 

 The latter is somewhat triangular in set'tion, having 

 above a shar]) edge, wliile lielow it is slightly hol- 

 lowed 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 ti)wards the base of the 

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

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

 tapei's rapidly in front t(»wards the narrowly rounded 

 frontal |iart. 



The cervical segnuuit is separated above from 

 the head b\- a very distinct and rather deej) hollow, 

 at the bottom of which nuiy I)e ti'aced a dis- 

 tiiu-t transverse sutiin' (see tig. 3) ending at eai-h 

 side in a liighl\' cliitinised ])rocess, to which the 

 upper ends of the mandibles are articulated. The 

 dorsal ]iart of the segnu'nt is considerably vaulteil, 

 and of abnost the same length as the head, the 

 \cntral ]iart. on the other hand, being very short, 

 and contined only to the space between the man- 

 dibles and the adductor mus(de of the shell. 



The body iii-o])er (trunk) (see tig. 1) is more 

 than twice as long as the 2 |)reccding sections 

 together, and almi)st cylindrical in shape, or only 

 verv slightly tapering bidiind. It is divided into a 

 series of very uniform segnu^nts, each bearing a 

 pair of liranchial legs. The nunil)er of segments in 

 full-grown inilividuals corresponds with the number 

 of branchial legs, viz fi-om 22 to 24, of which, 

 however, the hindmost is generally im|>erfectly 

 defined. .\11 the segnuMits, with the excejition of 

 the very foremost ones, have a bunch uf backward- 

 curved bristles aliove, those on the hindnmst seg- 



