Slide showing image of 'Limulus polyphemus'. Slide shows 'ventral view of Limulus polyphemus [horseshoe crab] x 1/2.' Labelled parts include: '1. cephalo thorax; 2. abdomen; 3. caudal spine; 4. chelicerae; 5-9. the five legs; 10. genital operculum (1st abdominal appendage); 11-15. branchiate appendages (abdominal appendages 2-5); 16. anus; 17. points to the region of the mouth; 18. chilaria (7th cephalothoracic appendages) (after Shipley and MacBride)'. Late 19th - early 20th century