STATE GEOLOGIST. 141 



(b) var. similis, (Var. n.) 



(Plate Q. Figs. 5—7.) 



This form is twice as large as D. leptopus, but otherwise scarcely 

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

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

 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 setae; the antenna reached 

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

 those of D. longicornis 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. Diaptomus laticeps, Sars. 



"CephalGthorax abtiee dilatatus, latidudine maxima in pane antica capitis sita, 

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

 lateralibus acuminatis. Segmentuni 1-mum abdominale feminse amice latum muerone 

 brevi laterali armatum, postice sensim attenuatum. Rami caudales sat magni seg- 

 menta antecentia 2 juncta longitudine iequantes setis brevissimis et robustis instruct!. 

 Antennse 1-mi paris feminse longltudinem corporis oequantes, animali natante rectse et 

 quam in D. gracili adliuc magis postice vergeates ; articulus antepenuitimus antennse 

 dextrse maris liamulo armatus. Ramus exterior autennarum 2-di paris interiore multo 

 longior articulo ultimo longitudinem articulorum antioedenttum 5 ajquante. Pedum 

 5-ti paris feminse articulus ultimus parvus, cylindricus, non vero tarn rudimentaris 

 quam in D. castore, aculeo uno brevi apicali instructus ; appendix interna ne tertiam 

 quidem longitudinis articuli 3-ti partem sequans et uniarticulata ; pedis dextri maris 

 articulus 3-tlus extrorsum aculeo forti armatus, ungue terminali valde flexuoso et sub- 

 sigmoides ; sinister aculeis duobus rectis terminatus. Saccus oviferus sat multa conti- 

 netova. Color pleurumque Isete cteruleus, interdum pallidior, albescens. Longit. 

 feminse circit. 154 mm." 



Sp. 8. Diaptomus gracilis, Sars. 



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

 latitudine maxima in medio sita. Anguli laminarum segmenti ultimi thoracalis femi- 

 nse in mucrones teuues et acuminatos producti, et muerone simili sat magno segmen- 

 tuna 1-raum abdominale utrinque armatus est. Kami abdominales breves setis in fe- 

 mlna valde divergentibus. Antennte 1-mi paris feminse perlongse et tenues, longitudi- 

 nem totius animalis longe superantes, animali natanti rectse et aliquantum postice ver- 

 gentes ; articulus antepenuitimus antennae dextrre maris hamulo longior, articulo ultimo 

 rami dimidium longitudinem sequante. Pedum 5-ti paris feminse articulus ultimus di- 

 stinctus, quadratus aculeis duobus apicalibus quorum interior apicem fere unguis arti- 

 culi penultimi attingit instructus ; appendix interna articulo 3-tio brevior ; unguis ter- 

 minalis pedis dextri maris apicem versus valde curvatus . Saccus oviferus semper ova 

 continet paucissima et magna regulariterque distributa. Animal pleurumque pelluci- 



