. A text-book of invertebrate morphology. Invertebrates. TYPE ORUaTACEA. 387 which may form a dorsal carapace, as in Apus, or a bivalved shell, as in Limnadia, Zimnetis, and EstJieria (Kg. 174), an adductor muscle being developed for the closure of the shell within which the entire body may be withdrawn. The anten- nules are as a rule small and are provided with olfactory hairs; the antennae, on the other hand, are well developed ex- cept in Apus, in which they are in some species quite small and in others entirely wanting. In the shelled forms they are biramous, consisting of a several-jointe
. A text-book of invertebrate morphology. Invertebrates. TYPE ORUaTACEA. 387 which may form a dorsal carapace, as in Apus, or a bivalved shell, as in Limnadia, Zimnetis, and EstJieria (Kg. 174), an adductor muscle being developed for the closure of the shell within which the entire body may be withdrawn. The anten- nules are as a rule small and are provided with olfactory hairs; the antennae, on the other hand, are well developed ex- cept in Apus, in which they are in some species quite small and in others entirely wanting. In the shelled forms they are biramous, consisting of a several-jointed protopodite termi- nated by two many-jointed tlagella, and serve as oarlike loco- motor organs, but in Branchipus they are short strong struc-. FiG. 174.—Esiheria compleximanus (after Packard). afi = antennule. afi = antenna. m = shell-muscle. tures without any locomotor function, serving in the males as clasping organs of use in copulation. The mandibles are reduced to toothed plates, lacking a palp, and the first max- illae show an almost similar reduction, while the second are entirely wanting in some genera, such as Zifnnetis. The suc- ceeding appendages are not limited to the thoracic region of the body, taking the genital opening as the limit between the two regions. Thus in Apus cancriformis there are eleven thoracic appendages, while behind the genital ring there are no less than over fifty locomotor limbs, and in such forms as Limnetis and Estheria (Fig. 174) it is difiicult to distinguish between the thorax and the anterior abdominal segments. The heart of the Branchiopoda is a more or less elongated organ with several ostia. and is usually limited to the anterior portion of the thoracic cavity, though in JBrancTiipus it extends. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original McMurrich, J. Pla
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1894
