To refer to this article use this url: http://dpc.uba.uva.nl/ctz/vol71/nr04/art06
Acknowledgement
We thank Jan van Arkel for graphic assistance. Prof. Derek Briggs and Dr. Jens Høeg offered valuable suggestions for improving the manuscript. We are further indebted to Dr. Jens Høeg for permitting us to use the illustrations of thecostracan lattice organs (Fig. 6).