348 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



This larva is colorless, excepting large spots of reddisb pigment, distributed much as in the 

 previous stage. There is a spot near the extremity of the eye-stalk and similar ones on the abdo- 

 men. Some of the appendages are also tipped with brownish red. The attainment of the adult 

 characters is now mainly a question of the further growth of parts already present. 



The above outline gives us a pretty complete history of the metamorphosis of Stenopus. 

 Between stages B and O a lacuna occurs, but it is not difiQcult to bridge over this gap. The 

 development of Stenopns is especially interesting, inasmuch as it combines certain features of the 

 metamorphosis of Penreus, Sergestes, Lucifer, and the Prawns in general, but it differs essentially 

 from any of them. Detailed comparisons are purposely omitted in this paper, but we will call 

 attention to the apparent similarity of the second larva of Stenopus (PI. viii. Fig. 17) to the zoea 

 of GalUanassa subterranea, figured by Claus.* The length iu each case is o"". He says, p. 54: 



Die juiifjeu Calliaoassa larveu besitzen beim Verlassen der Eihiillen eine ansehnliche Grijsse, sind sehr lauo;- 

 gestreckt nnd tragen drei spaltiistigc Fiisspaare, vou denen sich das Vordeie schon -n-eseutlich der Foimgestaltung 

 des spiiteren Maxillarfiissee nlibert. Der laiige Stirusebnabel, sowie die Bestaebehing des Abdomens, dessen zweites 

 Segment mit einem besouders laugeu Kiickendorn bewaft'uet ist erriDem an die nbeu beschriebeue larve. 



which applies perfectly to the Stenopus zoea, except that the latter has th« first thoracic segment 

 with its appendages, while, according to Claus, the first zoea of Callianassa has not, although his 

 figure is not clear on this, point. The rostrum, eyes, antenna;, second maxilhr, and maxillipeds 

 are nearly identical in the two forms. The differences are in the shape of the telson and in the 

 condition of the thoracic appendages. The tail fin has a convex posterior edge, a median and two 

 lateral, short spines, and eleven intermediate pairs. The rudiments of the sixth pair of abdomi- 

 nal appendages show through the integument. Behind the maxillipeds, already "die kurzen, 

 schlauchforniigen Anlagen sammtlicher Thoracalfiisse unter dem Integument bemiirkbar sind." 



Among the Prawns, Penseus has appajrently preserved most completely the ancestral history 

 of the Decapod Crustacea, and for this reason a thorough knowledge of the development of related 

 species is very desirable. 



IV. THE ADULT. 



Stenopus (Latreille). 



Cancer (Herbst). 



Palccmon (Olivier). 



Stenoprt.i (Latreille) L^ach, Desmarest, Eoux, Milne, Edwards, Adams, Dana, etc. 



Diagnosis of Stenopus hispidus (Latreille). — Body nearly cylindrical. Carapace -with prominent rostrum and 

 distinct transverse groove. Outer antennse -with long, bristle-bordered scale bent under the inner antennae 

 toTward the middle line. Second maxillipeds -with epipodite and long exopodite. Third maxillipeds very 

 long and appendicular, isrith a rudimentary exopodite at base. First, second, and third pairs of pereiopods 

 chelate. The first and second pairs quite slender, ending in small shears. Third pair longest, bearing the 

 large cla-ws. Fourth and fifth pairs of pereiopods slender and nonchelate. Carpus and propodus of the same 

 articulated into numerous rings. First pair of pleopods uniramous in both sexes, all the others biramous. 



Special description. — Length, 37-44™" (li-l^ inches). There is little diflerence in size between 

 the sexes, but the females are usually a trifle the larger. 



Color: Body invariably white, crossed by three bands of reddish crimson. Appendages col- 

 orless, excepting the third pair of i)ereiopods, which are encircled by four wide zones of the same 

 color. These markings are not of uniform tint, but vary from bright scarlet to mottled orange red. 

 The basal joints of at least the third and fourth pairs of thoracic legs sky blue. AntennjE snow 

 white. For further i)articulars under this heading, see PI. T, and Sec. i. 



The carapace (Fig. 37) ]>resents a marked transverse fossa. It is covered with .short dentiform 

 spines, largest on the front. The ro.'^trum is elevated, extending hardly beyond the basil joint of 

 the inner antenuiie. It ends in a sharp terminal si)ine and carries six to seven stout, curved teeth 

 on the dorsal median line, liesides a single spinule projecting downwards near the tip. From'the 

 single dorsal row of teeth two similar rows diverge, extending back to the transverse furrow. The 



*C. Claiia : " Untersiicbiingen znr Erforschung der genealogiscben Grundlage des Crustaceen-Systems." Wien, 

 1676. Taf. vm, Fig. 1 ; also Figs. -2-7. 



