. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. THE ANATOMY OF THE CAPE ROCK LOBSTER 137 (c) The heart (Figs 46-48, 50) The heart is elongate with sloping anterior margins and a rounded pos- terior extremity; it is a comparatively large, whitish, spongy organ, measuring about 20 mm long by 8 to 9 mm broad in medium-sized animals. As in other Decapoda, it is provided with three pairs of slit-like openings, the ostia (figs 31, 46-49, 53), through which the blood collected in the pericardial cavity enters the heart. The ostia are antero-dorsal, poste
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. THE ANATOMY OF THE CAPE ROCK LOBSTER 137 (c) The heart (Figs 46-48, 50) The heart is elongate with sloping anterior margins and a rounded pos- terior extremity; it is a comparatively large, whitish, spongy organ, measuring about 20 mm long by 8 to 9 mm broad in medium-sized animals. As in other Decapoda, it is provided with three pairs of slit-like openings, the ostia (figs 31, 46-49, 53), through which the blood collected in the pericardial cavity enters the heart. The ostia are antero-dorsal, postero-lateral, and ventral in position and, \vhile the dorsal ostia are directly obliquely forward and outward, the lateral ostia are more or less vertical and the ventral ostia are transverse. Each ostium is bordered by fairly wide, thin-walled lips, and closure of the opening is effected by contraction of a band of muscles along the free edge of each lip. The muscle bands of the two lips meet at the corners of the opening, and one overlaps the other before the muscle fibres pass into the wall of the heart. Inwardly projecting ostial valves, which have been reported in some Mala- costraca, were not observed. The heart is suspended in the pericardial cavity by groups of delicate elastic threads \vhich are associated with the expansion of the heart and the influx of blood during diastole. The fine strands constituting any one group usually arise in a common, short, narrow ligament secured to some particular part of the pericardial wall, but spread out and tend to interlace on their way to the heart. They are comparable to the alae cordis of Cancer (Pearson, 1908) and the suspensory ligaments oi Astacus (Baumann, 1921), and comprise anterior and posterior dorsal strands and six sets of fan-shaped lateral bands. As in Astacus, the anterior ligaments (figs 46, 47) are small, tough strips attached dorsally to the integument and inserted on either side of the root of the ophthalmic arte
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
