Ligamental structure in Mactracea and Myacea (Mollusca: Bivalvia)
In: Journal of the Marine Biological Association of the United Kingdom. Cambridge University Press/Marine Biological Association of the United Kingdom: Cambridge. ISSN 0025-3154; e-ISSN 1469-7769, more
|  |
| Abstract |
In the Bivalvia the two valves and connecting ligament are parts of a single shell each composed of three layers secreted by continuous surfaces of pallial epithelium as shown in Fig. 1. The superficial periostracum is formed in a groove at the base of the inner side of the outer (secretory) fold of the mantle margin and is continuous around the pallial lobes and within the embayments at each end of the ligament. The outer calcareous (prismatic) layer of the valves and the anterior and posterior outer (lamellar) ligament layers are formed by the outer surface of this outer fold which hypertrophies in the depths of the embayments where ligamental material is secreted. The inner calcareous (usually nacreous or porcellanous) layer of the valves is produced by the general pallial surface except along a mid-dorsal strip, the mantle isthmus (Owen, Trueman & Yonge, 1953; Yonge, 1953) which secretes the inner (fibrillar) ligament layer. |
|
