. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 250 bulletin: museum of comparative zoology. shell is mm. long as it lies in the matrix, but as the pygidium is somewhat bent under the body, the actual length is probably .5 mm. greater. The cephalon is 2 mm. long and 4 mm. wide (semicircular) and is bordered by a wdde (.5 mm.) concave brim. The glabella is convex, abruptly elevated above the brim at the front, bounded at the sides by deep dorsal furrows which converge backward. Between the eyes the glabella is marked by a pair of deep glabellar furrows. Be- hind
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 250 bulletin: museum of comparative zoology. shell is mm. long as it lies in the matrix, but as the pygidium is somewhat bent under the body, the actual length is probably .5 mm. greater. The cephalon is 2 mm. long and 4 mm. wide (semicircular) and is bordered by a wdde (.5 mm.) concave brim. The glabella is convex, abruptly elevated above the brim at the front, bounded at the sides by deep dorsal furrows which converge backward. Between the eyes the glabella is marked by a pair of deep glabellar furrows. Be- hind them, on the narrowest part of the glabella, is a median tubercle, and on each side at this point is an isolated basal lobe. In short, the glabella is like that of an adult specimen of Basilicus (Plate 1, fig. 1). The facial suture can not be made out with absolute certainty on these smallest specimens. On a specimen with the cephalon mm. long it seems to be marginal in front, while on a finely preserved cephalon 4 mm. long (No. 37), it is certainly intramarginal (Fig. 1). The eyes in the smallest specimens are very large, and only about one half their own length from the posterior margin. On a cephalon mm. long, the eyes are 1 mm. long and each forms a semicircle, the palpebral lobes almost touching the glabella in front. The posterior corner of the eye is only .3 mm. from the posterior mar- gin of the cephalon. The eye is there- fore relatively much larger than in the adult, but no further forward. The growth after this stage is more rapid in front of the eyes than behind them, and a cephalon 3 mm. long has the eyes still only 1 mm. long. The thorax of the smallest speci- mens shows feW' peculiarities other than the narrowness of the axial lobe. The specimen which is 3 mm. long has the axial lobe .5 mm. wide, or .2 the total width of the thorax. The smallest specimen with a well-preserved pygidium is mm. long, and the pygidium is mm. long and mm. wide.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1913
