STATE GEOLOGIST. 141 



(b) var. similis, (A"ar. n.) 

 (Plate Q. Figs. 5—7.) 



This form is twice as large as D. leptopus, but otherwise scarcel}' 

 distinguishable. It occurs in autumn (and spring?) in shallow 

 pools, which can but be frozen solid. The following diSereuces 

 are the only points yet noticed. Females of both of the species 

 were placed side by side upon a slide and examined. D. leptopus 

 measured 2.4 mm., exclusive of caudal setaj; the antenna reached 

 hardly to the base of the stylets; the eggs measured 0.12 mm., while 

 those of D. longicoruis measured 0.8 mm.; the egg-sac measured 

 0.8 mm., while that of longicornis was 0.5 mm. A few other minute 

 differences were noticed, but the general form and color was iden- 

 tical. The peculiar doubling of the edge of the last segment is 

 characteristic of these two forms; each has a small spine on either 

 side of the abdomen. The base of the inner ramus of left foot of 

 fifth pair of the male has a double series of spines. 



Sp. 7. Diaptoiiius laticeps, Sars. 



"Cephalothorax autice dilatatus, latidudine maxima in parte antica capitis sita, 

 postice sensim attenuatus, segmento ultimo feminai ad latera parum extante angulis 

 lateralibus acuniinatis. Segmeutuni 1-muiu abdominale femina; antice latum mucrone 

 brevl laterall arniatum, postice sensim attenuatum. Rami caudales sat magnl seg- 

 menta antecentia 2iuncta longitudluetv<luantes sells brevlsslmis et robustis instructl. 

 Antennae 1-mi parls femlnse longltudinem corporis requantes, anlmall natante rectse et 

 quam In D. graclll adliuc magis postice vergentes ; artlculus autepenultimus antennoe 

 dextraj maris liamulo armatus. Ramus exterior antennarum 2-dl paris interlore multo 

 longlor articulo ultimo longltudinem articulorum anticedeutlum 5 ajquante. Pedum 

 5-tl parls femlnse artlculus ultimus parvus, cylindricus, non vero tam rudimentaris 

 quara in D. castore, aculeouuo brevl apicall Instructus ; appendix interna ne tertiam 

 quldem longltudlnls articull 3-tl partem oequans et unlartlculata ; pedis dextri maris 

 artlculus 3-tIus extrorsum aculeo forcl armatus, ungue termlnall valde flexuoso et sub- 

 slgmoides ; sinister aculels duobus rectis terminatus. Saccus oviferus sat multa conti- 

 netova. Color pleurumque isete caeruleus, Interdum pallldior, albescens. Longlt. 

 femlnse clrcit. l'/^ mm." 



Sp. 8. Diaptomus gracilis, Sars. 



"Corpus quam in D. castore gracilius, ceplialotliorace et antice et postice attenuato, 

 latltudlne maxima In medio slta. Angull laminarum segmentl ultlml thoracalls feml- 

 nse in mucrones teuues et acumiuatos producti, et mucrone simili sat magno segmen- 

 tum 1-mum abdominale utrinque armatus est. Rami abdomlnales breves setis in fe- 

 mlna valde dlvergentlbus. Antenna;^ l-mi paris femlna? perlongse et tenues, longltudi- 

 nem totius animalis longe superantes, anlmall natantl recta et aliquantum postice ver- 

 gentes ; artlculus autepenultimus antenua dextra^ maris bamulo longlor, articulo ultuno 

 rami dimidlum longltudinem a?quante. Pedum 5-tl parls femina; articulus ultimus rii- 

 stlnctus, quadratus aculels duobus aplcalibus quorum interior aplcem fere unguis arti- 

 cull penultlmi attiugit instructus ; appendix interna articulo 3-tlo brevior ; unguis ter- 

 minalls pedis dextri maris aplcem versus valde curvatus. Saccus oviferus semper ova 

 continet pauclsslma et magua regularlterque distrlbuta. Animal pleurumque pellucl- 



